研究者データベース

野口 聡(ノグチ ソウ)
情報科学研究院 システム情報科学部門 システム融合学分野
准教授

基本情報

所属

  • 情報科学研究院 システム情報科学部門 システム融合学分野

職名

  • 准教授

学位

  • 博士(工学)(早稲田大学)

ホームページURL

J-Global ID

研究キーワード

  • 電力システム   電磁エネルギーシステム   科学的可視化技術   逆問題・最適化設計・経済性最適化   電磁界数値解析   Scientific Visualization   Optimization and Inverse Probrems   Numerical Analysis for Electromagnetics   

研究分野

  • ライフサイエンス / 医用システム
  • 情報通信 / 感性情報学
  • 情報通信 / ソフトコンピューティング
  • ものづくり技術(機械・電気電子・化学工学) / 電力工学

職歴

  • 2017年10月 - 現在 マサチューセッツ工科大学 Research Affiliate
  • 2004年04月 - 現在 北海道大学 准教授
  • 2017年08月 - 2017年09月 マサチューセッツ工科大学 客員研究員
  • 2016年12月 - 2017年07月 米国国立高磁場研究所 客員研究員
  • 2016年06月 - 2016年11月 マサチューセッツ工科大学 客員研究員
  • 2012年02月 - 2012年12月 マサチューセッツ工科大学 客員研究員
  • 1999年04月 - 2004年03月 広島大学 助手
  • 1998年05月 - 1999年03月 マサチューセッツ工科大学 客員研究員

学歴

  • 1996年04月 - 1999年03月   早稲田大学   大学院理工学研究科   電気工学専攻

所属学協会

  • 日本シミュレーション学会   International Compumag Society   IEEE   日本AEM学会   低温工学・超電導学会   電気学会   Cryogenics and Superconductivity Society of Japan   

研究活動情報

論文

  • So Noguchi, Teki Imai, Dongkeun Park, Seungyong Hahn, Yukikazu Iwasa
    SUPERCONDUCTOR SCIENCE & TECHNOLOGY 33 11 2020年11月 
    The screening current induced in rare-earth barium copper oxide (REBCO) tape generates an unwanted irregular magnetic field. The screening current-induced field (SCIF) is a challenging issue for MRI, NMR, and accelerators magnet composed of REBCO coils. A few FEM-based simulation methods have been proposed to estimate the SCIF; however, they require a long computation time. Recently, we have proposed a simple SCIF computation method based on the self and mutual inductances of REBCO pancake coils and screening current radial paths on the top and bottom of pancake coils. The accuracy of the proposed method is not excellent; however, the computation time is quite short. In this paper, we report an equivalent circuit model that includes the self and mutual inductances of a REBCO pancake coil and screening current radial path. Moreover, with this proposed method, we can compute the SCIF of no-insulation (NI) REBCO pancake coils, which is not the case with the previously proposed FEM-based simulation method. The proposed method has been validated by experimentation. The proposed method is available online.
  • Thomas Kurauchi, So Noguchi
    SUPERCONDUCTOR SCIENCE & TECHNOLOGY 33 10 2020年10月 
    The no-insulation (NI) winding technique greatly enhances the thermal stability of REBCO (REBa2Cu3Ox, RE = Rare Earth) pancake coils by avoiding burn-out and thermal runaway. The complicated electrical behaviors in NI REBCO pancake coils produce convoluted mechanical behaviors, so that some journal papers reported that high-field NI REBCO pancake coils were mechanically damaged during quench. To apply NI REBCO magnets for practical commercial use, it is important to understand the electromagnetic and mechanical behaviors of NI REBCO pancake coils in detail with both experiments and simulations. To clarify the electrical behaviors, a few simulation methods for NI REBCO pancake coils have been proposed; such as a simple RL parallel equivalent circuit. In these previous models, the radial current paths along the top and bottom of the pancake coils are represented as one current circuit path. However, since the radial current path of the bottom of one pancake coil is actually very close to that of the top of the next lowest coil, inductive behavior between these two paths appears. The simulation results show a probability that different amounts of radial current on the top and bottom of one pancake coil are carried during quench.
  • Soobin An, Kibum Choi, So Noguchi, Chaemin Im, Jeseok Bang, Uijong Bong, Jaemin Kim, Seungyong Hahn
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 30 4 2020年06月 
    When a quench occurs in a no-insulation (NI) high temperature superconductor (HTS) magnet that consists of a stack of double-pancake (DP) coils, a large amount of current is often induced in an NI DP coil that is electromagnetically coupled with neighboring DP coils. The large induced current leads to an excessive magnetic stress and occasionally damages the magnet. In this paper, we propose a new quench protection concept to reduce the amount of induced current in an NI HTS magnet. The key idea is to use resistive copper in order to absorb a portion of electromagnetic energy that is initially stored in the magnet before the quench. We tentatively name these resistive coils as a "magnetic dam" as they may slow down the electromagnetic quench propagation speed among the NI DP coils, which may be beneficial to avoid over-stressing by the large over-current.
  • So Noguchi, Takahiro Tatsuta, Daisuke Nishikawa, Hiroshi Ueda, SeokBeom Kim
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 30 4 2020年06月 
    No-insulation (NI) (RE)Ba tex-math notation="LaTeX">$_3$ (REBCO) magnets are very promising for practical applications to generate high magnetic field. The NI winding technique provides high thermal stability so that quench protection is unnecessary. However, the turn-to-turn contact resistance (sometimes called characteristic resistance) is an important factor to characterize the thermal stability and charging delay of NI REBCO pancake magnets. Although the conventional sudden-discharging method is widely used to measure the turn-to-turn contact resistance, it is not applicable to various conditions; e.g., the change of DC operating current and temperature. Therefore, we have previously proposed a turn-to-turn contact resistance measurement method using a low-frequency AC (LFAC) current. In this paper, we measured the contact resistance for different DC operating currents or change of DC current to confirm the validity of LFAC method. In addition, by heating a test coil, the contact resistances were also measured during the change of DC operating current. Since the electromagnetic stress is small enough not to change the contact condition, the change in contact resistance is negligible. The measured contact resistance was unchanged, so we could conclude that the LFAC method is effective in measurement of the contact resistance when DC operating current was applied.
  • Haruka Onoshita, Yuka Yoshihara, Hiroshi Ueda, So Noguchi, Atsushi Ishiyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 30 4 4702605  2020年06月 [査読有り][通常論文]
     
    The no-insulation (NI) coil is a technology expected to realize both high current density and high thermal stability which are essentially trade-off relationship in REBCO coil application. This technique has been studied mainly for application to small-diameter inner coils of NMR magnets exceeding 30 T. In this case, the coil is cooled using 4.2-K liquid He. We are developing an NI-REBCO coil system for high-magnetic-field whole-body MRI, and for a medical cyclotron to be used for cancer therapy. The NI-REBCO coil which we aim for development has a diameter of similar to 1 m, a generated magnetic field is similar to 10 T, and a conduction cooling around 30 K is assumed. Because the size, operating temperature, and magnetic field differ from those of NMR coil, it is possible that the electromagnetic, thermal, and mechanical behaviors will be quite different. In this paper, we report on these behaviors when a local deterioration occurs in NI-REBCO double-pancake coils using numerical analysis considering coil size, operating temperature, and magnetic field as parameters. For the numerical simulation, we conducted a coupled analysis of current distribution analysis based on PEEC (Partial Element Equivalent Circuit) model and thermal analysis by the 2-dimensional finite element method.
  • Mincheol Cho, So Noguchi, Jeseok Bang, Jaemin Kim, Uijong Bong, Jung Tae Lee, Soo Bin An, Kabindra R. Bhattarai, Kwangmin Kim, Kwanglok Kim, Chaemin Im, Ki Jin Han, Seungyong Hahn
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 29 5 2019年08月 [査読有り][通常論文]
     
    This paper presents a "combined" circuit model to simulate non-linear behaviors of a no-insulation (NI) high temperature superconductor (HTS) coil. The key idea is a selective use of either the lumped circuit model or distributed depending on an operating condition. When the NI coil current is below its critical current, the radial leak currents through turn-to-turn contacts may be assumed to be uniformly distributed over the entire coil, thus, the lumped circuit model may suffice to analyze the NI behaviors. When the coil current increases beyond the critical current, the distributed model plays the role to simulate the spatial distribution of currents, both radial and azimuthal. By limiting the use of the time-consuming distributed model only for the post-quench part, the combined model enables substantial reduction in calculation time without sacrificing simulation accuracy. To verify the validity of the combined model, an over-current charging test of an NI HTS coil was simulated with the lumped, distributed, and combined models. The simulation results of the combined model are barely discernible from those of the distributed model, and agreed well with the measured ones as well. The results validate the combined model for more efficient simulation of an NI HTS coil.
  • So Noguchi, Ryousuke Miyao, Haruyoshi Okusa, Takahiro Tatsuta, Hiroshi Ueda, SeokBeom Kim
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 29 5 2019年08月 [査読有り][通常論文]
     
    The turn-to-turn contact resistance (characteristic resistance) is a very important factor to a no-insulation (NI)(RE)Ba-2 Cu3Oy (REBCO) pancake coil. It characterizes the stability and charging delay of NI REBCO pancake coils. However, the ordinary sudden-discharging method cannot measure the turnto-turn contact resistance under different conditions, such as an operating current, a temperature, and an external magnetic field. Although the turn-to-turn contact condition is strongly affected by the pressure inside of the NI REBCO coils, the feature of the contact resistance must he clarified to estimate the stability of NI REBCO coils. In this paper, we have proposed a new method to measure the turn-to-turn contact resistance applying ac current. The theory and the measurement results are also shown. The measured turn-to-turn contact resistance is reasonable, compared with that measured by the ordinary sudden-discharging method. In near future, we will measure the turn-to-turn contact resistance under different conditions by means of the proposed method.
  • Hiroshi Ueda, Atsushi Ishiyama, So Noguchi, Tomonori Watanabe, Shigeo Nagaya, Jun Yoshida, Mitsuhiro Fukuda
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 29 5 2019年08月 [査読有り][通常論文]
     
    In autumn 2017, the project "Quantum Innovation for Safe and Smart Society (QiSS)" was started in Program on Open Innovation Platform with Enterprises, Research Institute and Academia (OPERA) by Japan Science and Technology Agency (JST). One of the key issues of this project is the advancement of compact cyclotron and beam irradiation device for stable supply of short-lived radioisotope (RI). We proposed the air-core cyclotron using high-temperature superconducting (HTS) technology, named Skeleton Cyclotron, as high intensity compact cyclotron. Currently, we are carrying out a feasibility study on a variable-energy multi-particle Skeleton Cyclotron for RI production. In this paper, key issues in HTS magnet technologies for Skeleton Cyclotron and the preliminary conceptual design of variable-energy multi-particle Skeleton Cyclotron are reported.
  • So Noguchi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 29 5 2019年08月 [査読有り][通常論文]
     
    The no-insulation (NI) winding technique drastically enhances the thermal stability of REBa2Cu3Oy (REBCO) coils. Even if a larger current than a critical current is carried in NI REBCO pancake coils, the coils would not burn out. So far, many NI REBCO pancake coils showed a "self-protecting" characteristic in experiments. However, most of these experiments have been done under a low magnetic field or cooled by liquid nitrogen. Under these conditions, a huge electromagnetic force does not occur after an NI REBCO pancake coil transitions into a normal state. Recently, the NI winding technique has been applied to high-field magnets, such as NMR and accelerators. Under a high magnetic field (> 20 T), a huge hoop stress is generated after one NI REBCO pancake coil constituting a high-field magnet by stacking reaches to quench. The huge hoop stress causes the delamination of REBCO-coated conductors. That is, the quench protection condition of high-field NI REBCO magnets is decided according to the mechanical condition, even though the magnets show a high thermal stability. In this paper, three simulation models for NI REBCO pancake coils are compared, and then the mechanical condition is discussed for a quench protection through an electromagnetic, thermal, and mechanical simulation of multistacked NI REBCO pancake coils for high field generation.
  • Yuta Kakimoto, Tetsuri Ichikawa, Haruka Onoshita, Tetsuro Kinpara, Atsushi Ishiyama, So Noguchi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 29 5 2019年08月 [査読有り][通常論文]
     
    We previously developed a high-magnetic-field REBCO coil for use in medical devices such as medical accelerators and high-magnetic-field MRI. The use of high-temperature superconducting (HTS) coils in such applications necessitates their miniaturization while providing high magnetic fields. However, when the current density is improved by reducing the copper-stabilization-layer thickness in the conventional insulated HTS coil, the thermal stability is lowered, which leads to a tradeoff between high current density and high thermal stability. Therefore, we examine noinsulation (NI) coils that allow compatibility between high current density and thermal stability. Recent research has indicated that NI coils with multiple defects can afford a stable and high critical current (Ic) and operate without serious problems, which makes it possible to produce coils wound with commercial REBCO tapes containing several defects along the tape, which in turn makes fabrication economically viable. However, there are many unknown aspects of the current, magnetic field, and heat behaviors of NI coils with defects, particularly when large currents flow through them. Here, in order to examine the behavior of a multiple-defect NI coil subjected to a large current at the temperature of similar to 30 K via application of the conduction cooling method, we use a combination of the partial element equivalent circuit method and the finite-element method to investigate the detailed current and thermal behaviors. Our results indicate that defective NI coils can afford a critical current Ic value of similar to 80% of that of defect-free NI coils, which makes our findings valuable in terms of contributing to further developments in HTS coil applications.
  • Tetsuri Ichikawa, Yuta Kakimoto, Haruka Onoshita, Tetsuro Kinpara, So Noguchi, Shigeo Nagaya, Tomonori Watanabe, Atsushi Ishiyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 29 5 2019年08月 [査読有り][通常論文]
     
    No-insulation (NI) coils are an important technique for high-field magnetic resonance imaging (MRI). One of the technical issues with NI coils is their thermal and electromagnetic behavior when a local normal transition occurs. Given that multiple stacked coils are used in MRI, the interaction between coils must also be investigated, because a local normal transition may affect the other NI coils through magnetic coupling. In fact, when a local normal transition occurs, there is a possibility that large electromagnetic forces are applied to the other coils, or quench may be induced in some of them. Even though overcurrent tests of stacked NI coils have been conducted, the results are not helpful in actual MRI operation. In this study, we investigate the effects of the occurrence of a local normal transition in multi-stacked NI coil systems under conditions similar to those of actual operation, with a constant transport current below the coil's I- c. The occurrence of a local normal transition is simulated by applying current to a heater inserted in manufactured small NI double pancake coils. To evaluate the interaction between NI coils, the voltage and changes in the generated magnetic field are measured at each evil. We also show the current distribution in the coils, as obtained by the partial element equivalent circuit method. The obtained results allow us to evaluate the interaction of the NI coils and evaluate coil protection methods.
  • Philip C. Michael, Dongkeun Park, Yoon Hyuck Choi, Jiho Lee, Yi Li, Juan Bascunan, So Noguchi, Seungyong Hahn, Yukikazu Iwasa
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 29 5 2019年08月 [査読有り][通常論文]
     
    We present assembly and test results of a 3-nested-coil 800-MHz (18.8 T) REBCO insert (H800) for the MIT 1.3 GHz LTS/HTS NMR magnet currently under completion. Each of the three H800 coils is a stack of no-insulation (NI) REBCO double-pancake coils (DPs). The innermost 8.7-T Coil 1 (26 DPs) was completed by mid-2016; the middle 5.6-T Coil 2 (32 DPs) was completed in mid-2017; while the outermost 4.5-T Coil 3 (38 DPs) was completed in early 2018. Coils 1, 2, and 3 were assembled together in early 2018 as a 3-nested-coil, the H800, and tested, first in liquid nitrogen to a power supply current of 20 A, followed by testing in liquid helium to a power supply current of 251.3 A, the H800's design operating current. After roughly five minutes settling time at 251.3 A, the H800 quenched. In this paper, we examine probable sources of quench initiation and simulate ensuing quench behavior. Remedial efforts to minimize the tendency toward quenching in the H800 are presented and discussed.
  • So Noguchi, Dongkeun Park, Yoonhyuch Choi, Jiho Lee, Yi Li, Philip C. Michael, Juan Bascunan, Seungyong Hahn, Yukikazu Iwasa
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 29 5 2019年08月 [査読有り][通常論文]
     
    The MIT 1.3-GHz LTS/high-temperature superconducting (HTS) nuclear magnetic resonance (NMR) magnet is currently under development. The unique features of this magnet include a three-nested formation for an 800-MHz REBa2Cu3Ox. (RE = Y, Gd) (REBCO) insert (H800) and the no-insulation (NI) winding technique for H800 coils. Because when it is driven to the normal state, an NI REBCO magnet will respond electromagnetically, thermally, and mechanically that may result in permanent magnet damage, analysis of a quenching magnet is a key aspect of HTS magnet protection. We have developed a partial element equivalent circuit method coupled to a thermal and stress finite-element method to analyze electromagnetic and mechanical responses of a nested-coil REBCO magnet each a stack of NI pancake coils. Using this method, quench simulations of the MIT 1.3-GHz LTS (L500)/HTS (H800) NMR magnet (1.3G), we have evaluated currents, strains, and torques of H800 Coils 1 to 3 and L500, and center fields of 1.3G, L500, and H800. Our analyses show H800 is vulnerable to mechanical damage.
  • Seungyong Hahn, Kwanglok Kim, Kwangmin Kim, Xinbo Hu, Thomas Painter, Iain Dixon, Seokho Kim, Kabindra R. Bhattarai, So Noguchi, Jan Jaroszynski, David C. Larbalestier
    NATURE 570 7762 496 - + 2019年06月 [査読有り][通常論文]
     
    Strong magnetic fields are required in many fields, such as medicine (magnetic resonance imaging), pharmacy (nuclear magnetic resonance), particle accelerators (such as the Large Hadron Collider) and fusion devices (for example, the International Thermonuclear Experimental Reactor, ITER), as well as for other diverse scientific and industrial uses. For almost two decades, 45 tesla has been the highest achievable direct-current (d.c.) magnetic field; however, such a field requires the use of a 31-megawatt, 33.6-tesla resistive magnet inside 11.4-tesla low-temperature superconductor coils(1), and such high-power resistive magnets are available in only a few facilities worldwide(2). By contrast, superconducting magnets are widespread owing to their low power requirements. Here we report a high-temperature superconductor coil that generates a magnetic field of 14.4 tesla inside a 31.1-tesla resistive background magnet to obtain a d.c. magnetic field of 45.5 tesla-the highest field achieved so far, to our knowledge. The magnet uses a conductor tape coated with REBCO (REBa2Cu3Ox, where RE = Y, Gd) on a 30-micrometre-thick substrate(3), making the coil highly compact and capable of operating at the very high winding current density of 1,260 amperes per square millimetre. Operation at such a current density is possible only because the magnet is wound without insulation(4), which allows rapid and safe quenching from the superconducting to the normal state(5-10). The 45.5-tesla test magnet validates predictions11 for high-field copper oxide superconductor magnets by achieving a field twice as high as those generated by low-temperature superconducting magnets.
  • So Noguchi, Seungyong Hahn, Atsushi Ishiyama, Yukikazu Iwasa
    SUPERCONDUCTOR SCIENCE & TECHNOLOGY 32 4 2019年04月 [査読有り][通常論文]
     
    No-insulation (NI) and metal-insulation (MI) winding techniques are promising for enhancing the thermal stability of REBCO pancake coils, toward the practical use of nuclear magnetic resonance and magnetic resonance imaging systems. The NI and MI REBCO pancake coils showed high thermal stability in many over-current tests. However, a disadvantage is a charging delay due to low turn-to-turn contact resistance. Therefore, many researchers have tried to increase turn-to-turn contact resistance to overcome the charging delay problem. Meanwhile, a partial element equivalent circuit (PEEC) model can accurately simulate the over-current and charging/discharging tests of NI REBCO pancake coils in detail. Using the PEEC model coupling with thermal finite element analysis (FEA), the thermal stability was evaluated during a local normal-state transition. From the simulation results, it was found that a best range of turn-to-turn contact resistance existed to keep a high thermal stability during a local normal-state transition. However, the PEEC and thermal FLA method requires a substantial amount of time with complicated simulation approach. In this paper, we propose a simple mathematical formulation to obtain an appropriate range of turn-to-turn contact resistance during a local normal-state transition, supposing a worst cooling condition. The simple computation is easy to use and timesaving to roughly estimate the operation reliability of NI REBCO pancake coils.
  • So Noguchi, Hiroshi Ueda, Seungyong Hahn, Atsushi Ishiyama, Yukikazu Iwasa
    SUPERCONDUCTOR SCIENCE & TECHNOLOGY 32 4 2019年04月 [査読有り][通常論文]
     
    The development of NMR/MRI REBa2Cu3Oy (REBCO, RE = rare earth) magnets is happening all over the world. It has been found that screening current-induced magnetic fields (SCMFs) are a serious problem for NMR/MRI magnets wound with REBCO tapes. The reduction of SCMFs is strongly desired, and the estimation of SCMFs is also desired at the design stage of REBCO magnets. In order to evaluate a SCMF, a finite element method (FEM) or a boundary integration method is needed thus far, and a high-level simulation technique is required. In this paper, we develop an easy method to estimate a SCMF without a high-level simulation technique. In this method, the inductance of a winding turn is calculated and then a screening current is estimated according to the magnetic field penetrating into the winding turn. The SCMF is obtained from the estimated screening current. The SCMFs computed by the proposed method were compared with measurements and simulation results of the FEM. The results agreed well, but we can see a large difference. However, the SCMFs found by the proposed method are accurate enough to know they are at the design stage without the use of a high-level simulation technique.
  • 伊東 慶太, 植田 浩史, 野口 聡, 石山 敦士
    低温工学 54 2 119 - 126 2019年03月 [査読有り][通常論文]
  • Ryosuke Miyao, Hajime Igarashi, So Noguchi
    INTERNATIONAL JOURNAL OF APPLIED ELECTROMAGNETICS AND MECHANICS 59 1 181 - 189 2019年 [査読有り][通常論文]
     
    This paper presents the current and thermal phenomena of multi-stacked No-Insulation (NI) REBa2 Cu3O7-x (REBCO, RE = Rare Earth) pancake coils during a local normal-state transition. An NI winding technique is expected to enhance the thermal stability of REBCO pancake coils, and it was verified in numerical simulations on a single pancake coil. However, a multi-stack of pancake coils are used to generate a high magnetic field in practical applications. When a normal-state transition occurs in one of multi-stacked pancake coils, it may deteriorate the stability of the other pancake coils. Therefore, we have developed a numerical simulation code to clarify the current and thermal behaviors of multi-stacked NI REBCO pancake coils using a partial element equivalent circuit model and a thermal finite element method.
  • So Noguchi, Seungyong Hahn
    31ST INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS2018) 1293 2019年 [査読無し][通常論文]
     
    This paper presents the unbalanced torque generated in No-Insulation (NI) REBa2Cu3Ox (REBCO, RE = Rare Earth) pancake coils after a normal-state transition. The NI REBCO pancake coil has a high thermal stability, and it is desired to apply to ultra-high field magnets. When an NI REBCO pancake coil locally transitions into a resistive state, the operating current bypasses a normal-state-transitioned turn to adjacent turns in the coil-radial direction, and the amount of heat generation can be reduced. That is an inherent feature of NI REBCO pancake coils. However, when a radial current flows in a magnetic field, a Lorentz force is generated toward the coil-circumferential direction, i.e. torque. In case that the coil radius and the external magnetic field are very large, the extremely large torque is generated, and it could damage the magnet itself and/or the joints to terminals with a mechanical factor. Therefore, it is necessary to investigate the behavior of the torque generated in the NI REBCO pancake coil after the quench.In this paper, we present the numerical simulation results of the behaviors of the torque generated in the NI REBCO double pancake coil after quench. Their current, thermal, and mechanical behaviors are simulated by a partial element equivalent circuit (PEEC) method and 2-D thermal finite element method (FEM). The behaviors are different depending on the coil size. In addition, the behavior is presented when the operating current is suddenly shut down after quench.
  • 伊東慶太, 植田浩史, 野口聡, 石山敦士
    低温工学 54 2 119‐126(J‐STAGE)  2019年 [査読無し][通常論文]
  • So Noguchi, Kwangmin Kim, Seungyong Hahn
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 28 3 2018年04月 [査読有り][通常論文]
     
    The no-insulation (NI) winding technique is one of the most promising high-temperature superconducting (HTS) coil protection methods to realize the practical use of HTS magnets. Many NI REBa2Cu3O7-x (REBCO, RE = Rare Earth) magnets have been developed to generate ultrahigh magnetic fields for NMR or MRI magnets. When NI REBCO magnets are operated in a high magnetic field, uncommon phenomena can be observed, because the NI REBCO magnets have multicomplicated current paths. An unexpected voltage rise was experimentally observed during charging NI coils or after quench. The cause of such a voltage rise cannot be explained by means of a partial element equivalent circuit method, which was proposed to clarify such complicated current behavior. We think one of causes is an electric field generation by Hall effect. In this paper, therefore, we will investigate the electrical field behavior of NI REBCO coils by Hall effect. An unforeseen voltage would appear between terminals.
  • Jiho Lee, Dongkeun Park, Philip C. Michael, So Noguchi, Juan Bascunan, Yukikazu Iwasa
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 28 3 2018年04月 [査読有り][通常論文]
     
    In this paper, we present experimental results of a small-model study, from which we plan to develop and apply a full-scale field-shaking system to reduce the screening-current-induced field (SCF) in the 800-MHz high-temperature superconducting (HTS) Insert (H800) of theMIT 1.3-GHz low-temperature superconducting (LTS)/HTS nuclear magnetic resonance magnet (1.3 G) currently under construction-the H800 is composed of three nested coils, each a stack of no-insulation (NI) REBCO double pancakes (DP). In 1.3 G, H800 is the chief source of a large error field generated by its own SCF. To study the effectiveness of the field-shaking technique, we used two NI REBCO DPs, one from Coil 2 (HCoil2) and one fromCoil 3 (HCoil3) of the three H800 coils, and placed them in the bore of a 5-T/300-mm room-temperature bore LTS background magnet. The background magnet is used not only to induce the SCF in the DPs, but also to reduce it by the field-shaking technique. For each run, we induced the SCF in the DPs at an axial location where the external radial field BR >0, and then, for the field shaking, moved them to another location where the external axial field Bz >> B-R. Due to the geometry of H800 and L500, top DPs of three H800 coils will experience the considerable radial magnetic field perpendicular to the REBCO tape surface. To examine the effect of the field shaking on the SCF, we tested each NI REBCO DP in the absence or presence of a radial field. In this paper, we report 77-K experimental results and analysis of the effect and a few significant remarks of the field shaking.
  • Ryosuke Miyao, Hajime Igarashi, Atsushi Ishiyama, So Noguchi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 28 3 2018年04月 [査読有り][通常論文]
     
    This paper presents the thermal and electromagnetic behaviors of multistacked no-insulation (NI) REBa2Cu3O7-x (REBCO, RE = rare earth) pancake coils. The NI winding technique gives a high enough thermal stability not to damage REBCO coils even though a normal-state transition occurs. The high thermal stability has been verified through overcurrent tests. Moreover, the numerical simulation of multistacked NI REBCO pancake coils has been performed to investigate the electromagnetic behaviors in detail. The simulation results also confirmed the high thermal stability of NI REBCO pancake coils. However, it does not mean that an NI REBCO magnet never quenches. In experiments, it was observed that a quench in one of the pancake coils propagated to the other pancake coils sequentially. The above sequential quench from pancake to pancake has not been confirmed in the numerical simulation since the thermal behavior is not considered. For the more reliable verification, we have developed a numerical simulation to investigate the thermal and electromagnetic behaviors by the partial element equivalent circuit method and the two-dimensional thermal finite-element method. In this paper, the six-stacked NI REBCO pancake coil is simulated with several operating temperatures, and the sequential quench is reproduced. The velocity of the sequential quench is also shown.
  • So Noguchi, Seungyong Hahn, Hiroshi Ueda, SeokBeom Kim, Atsushi Ishiyama
    IEEE TRANSACTIONS ON MAGNETICS 54 3 2018年03月 [査読有り][通常論文]
     
    Superconducting magnets wound with second-generation high-temperature superconductors, i.e., REBa2Cu3O7-x (REBCO, RE = Rare Earth) tapes, are desired to apply high magnetic field nuclear magnetic resonance, MRI, and accelerators. However, a major problem for practical application is an undesirable irregular magnetic field caused by screening currents induced in REBCO tapes. To investigate the screening current-induced magnetic field, a few simulation methods have been proposed. One of the effective simulation methods employs a finite-element method with a thin approximation method. Although the thin approximation method was developed to simulate eddy currents in magnetic steel sheets, and it is not applicable to REBCO tapes carrying a transport current. Therefore, the thin approximation method is extended to simulate screening currents in REBCO tapes considering a carrying transport current. To show the validity of the proposed extended thin approximation method, the screening currents of an REBCO magnet are computed, and the results are compared with the measurement and simulation results of the conventional thin approximation method. The more accurate solution is available by using the proposed methods.
  • So Noguchi, Shinya Matsutomo, Vlatko Cingoski
    IEEE TRANSACTIONS ON MAGNETICS 54 3 2018年03月 [査読有り][通常論文]
     
    We have previously been proposed a novel adaptive finite-element method (FEM) based on a magnetic field conservation indicator and a non-conforming mesh-refinement technique. However, we have applied to a very simple model consisting of a single permanent magnet for basic verification of the proposed method. In this paper, we have improved an error indicator, and tried to apply a newly proposed adaptive FEM to more complicated models, where ferromagnetic material is included. The newly proposed method is superior in torque error estimation to the Zienkiewicz-Zhu error estimation method in a 3-D permanent magnet motor model.
  • So Noguchi, Ryosuke Miyao, Katsutoshi Monma, Hajime Igarashi, Hiroshi Ueda, Atsushi Ishiyama
    IEEE Transactions on Applied Superconductivity 27 4 2017年06月 [査読無し][通常論文]
     
    © 2017 IEEE. This paper presents the current behavior and axial Lorenz force of stacked no-insulation (NI) REBa2Cu3O7-x (REBCO, RE = Rare Earth) double-pancake coils during local normal-state transition. The NI winding technique enhances the thermal stability and increases the engineering current density in REBCO pancake coils. The high thermal stability of NI REBCO coil has been verified in experiments of overcurrent test. In addition, the numerical simulations of NI REBCO single-pancake coils have been performed to confirm the high stability. However, REBCO magnets usually consist of some stacked double-pancake coils to generate a high magnetic field for practical applications. When a normal-state transition occurs in one of the stacked pancake coils, it may affect the other pancake coils. For the more reliable verification, the current and electromagnetic force behavior of stacked NI REBCO pancake coils during a normal-state transition should be simulated. To examine the stacked NI REBCO pancake coils, we extend the previously proposed partial element equivalent circuit (PEEC) model to deal with a few double-pancake coils. In this paper, an NI REBCO double-pancake coil and their three stacked coils are simulated by using the extended PEEC model.
  • Hiroshi Miyazaki, Sadanori Iwai, Tatsuro Uto, Yasumi Otani, Masahiko Takahashi, Taizo Tosaka, Kenji Tasaki, Shunji Nomura, Tsutomu Kurusu, Hiroshi Ueda, So Noguchi, Atsushi Ishiyama, Shin-Ichi Urayama, Hidenao Fukuyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 27 4 2017年06月 [査読有り][通常論文]
     
    Superconducting magnets for magnetic resonance imaging systems require homogeneous, stable magnetic fields. The homogeneity of the magnetic field is highly dependent on the coils shape and positions. Furthermore, in REBa2Cu3O7-delta (REBCO) magnets, the screening-current-induced magnetic field, which changes the magnetic field distribution of the magnet, is one of the most critical issues. In the work described here, a small REBCO coil that can generate a magnetic field of over 10 T was fabricated and tested. The small REBCO coil was composed of a stack of 22 single pancake coils whose inner and outer diameters were 50 mm and 130 mm, respectively. The total conductor length was 1.5 km. The small REBCO coil could generate a central magnetic field of 8.27 T at 10 K. A magnetic field of over 10 T was achieved by replacing 12 of the single pancake coils with new ones wound with the latest REBCO-coated conductors. The measured value of the central magnetic field at 10 K was 13.53 T, which was lower than the calculated value of 13.94 T obtained without taking account of the screening-current-induced magnetic field. Furthermore, it was examined whether the current sweep reversal would be effective for 10 T-class magnetic field conditions.
  • Hiroshi Miyazaki, Sadanori Iwai, Tatsuro Uto, Yasumi Otani, Masahiko Takahashi, Taizo Tosaka, Kenji Tasaki, Shunji Nomura, Tsutomu Kurusu, Hiroshi Ueda, So Noguchi, Atsushi Ishiyama, Shin-ichi Urayama, Hidenao Fukuyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 27 4 2017年06月 [査読有り][通常論文]
     
    We started developing REBa2Cu3O7-delta (REBCO) magnets for ultrahigh-field magnetic resonance imaging (MRI) systems in 2013. Our final targets are 9.4 TMRI systems for whole-body and brain imaging. In this paper, a conduction-cooled 1.5 T REBCO MRI magnet having a room-temperature bore of 396 mm was fabricated and tested in order to evaluate the magnetic field homogeneity and stability. The magnet was composed of 60 single pancakes whose inner diameter was 500 mm. The total conductor length was 10.3 km, and the total inductance was 12.4 H. The size of the homogeneous magnetic field region was 200 mm diameter spherical volume. The central magnetic field was as high as 1.5 T at 192.7 A, and the current density of single pancakes was 301 A/mm(2). The magnet was cooled from room temperature to 4.7 K in 55 hours, and the temperature difference among the coils was 0.1 K or less during both initial cooling and excitation. The magnetic field inhomogeneity was 249.7 parts per million (ppm), and the Z(2) coefficient was largest at 579.6 ppm. The main reason for the error magnetic field was dimensional errors in the positions on the z-axis. The magnetic field inhomogeneity was improved to 4.1 ppm by passive shimming using iron pieces. The magnetic field stability was about 2 ppm/h because of a reduction in screening-current induced in the REBCO-coated conductors. Current sweep reversal improved the magnetic field stability from 2 ppm/h to 0.8 ppm/h.
  • So Noguchi, Ryosuke Miyao, Katsutoshi Monma, Hajime Igarashi, Atsushi Ishiyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 27 4 2017年06月 [査読有り][通常論文]
     
    No-insulation (NI) REBCO pancake coils show high thermal stability, however the charging delay is an issue. Hence, to improve the charging delay, it was proposed that a stainless steel (SUS) tape was cowound between turns, called "metal-as-insulation" or "metal-insulation (MI)," to increase the turn-to-turn contact resistivity. The MI technique could make the turn-to-turn contact resistivity approximately 50 times large compared to a conventional NI REBCO pancake coil. This paper reports a bypass current behavior on the cross section of MI REBCO pancake coil using two-dimensional finite element method. The influence of the SUS tape thickness, the MI material, and the number of SUS tapes on the turn-to-turn contact resistivity is investigated. As the result, it is clarified that the turn-to-turn contact resistivity strongly depends on the surface condition and number of SUS tapes.
  • Tao Wang, Kazuki Katsumata, Atsushi Ishiyama, So Noguchi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 27 4 2017年06月 [査読有り][通常論文]
     
    In this paper, we have proposed a detection method for detecting and locating a local normal-state transition in a meter-class no-insulation (NI) coil that is deployed in next-generation high-field magnetic resonance imaging scanners (MRIs), using a copper pickup coil. There are two schemes for detecting and locating the normal zone: one is a ring pickup coil assembled on the midplane of a central bore and the other consists of several sector pickup coils deployed on the coil winding, namely "scanning pickup coil." To verify the effectiveness of these detection methods, we performed a numerical simulation coupling consisting of a partial element equivalent circuit, a thermal analysis, and a magnetic field analysis. Based on the results of analyses, we reproduced the distributions of the temporal variations of the magnetic flux in the central bore and on the coil winding of the meter-class NI coil, and discussed the effectiveness of these pickup coil schemes for detecting and locating a local normal-state transition in a meter-class NI coil used in next-generation high-field MRIs.
  • Shinya Matsutomo, Tomohisa Manabe, Vlatko Cingoski, So Noguchi
    IEEE TRANSACTIONS ON MAGNETICS 53 6 2017年06月 [査読有り][通常論文]
     
    An immersive real-time visualization system of 3-D magnetic field for educational purposes is presented. This immersive visualization system is based on augmented reality technology. The proposed system provides observation of a magnetic field distribution and its stereoscopic vision in 3-D space using head mounted display. To improve the visualization capabilities, a new real-time method for drawing magnetic flux lines in 3-D space is developed and presented in this paper. It enables a user to easily observe and grasp a magnetic field generated by multiple sources (e.g., magnets and/or multiple coils) in an augmented 3-D space. Additionally, it permits a user to freely and interactively move the magnetic sources within the visualization space and to observe the magnetic fields interference in real-time. As a result, one can intuitively and easy visualize, observe and grasp the magnetic field even in 3-D space.
  • Kazuki Katsumata, Tao Wang, Atsushi Ishiyama, So Noguchi, Katsutoshi Monma, Shigeo Nagaya, Tomonori Watanabe
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 27 4 2017年06月 [査読有り][通常論文]
     
    Inmagnetic resonance imaging and nuclear magnetic resonance applications, it is important that the high-temperature superconducting coils provide a high magnetic field in a miniaturized form factor. Our research group considers these requirements to be compatiblewith no-insulation (NI) coils in which the thickness of the Cu stabilization layer and the turn-to-turn contact electrical resistance are key parameters that enable both high current densities and high thermal stabilities. When the Cu stabilization layer is thin, the current density is impaired, but the thermal stability is improved. If the turn-to-turn contact electrical resistance is very large, then the characteristics of the NI REBCO coil approach the characteristics of conventional insulated coils, and the thermal stability may be degraded. However, when the turn-to-turn contact electrical resistance is large, the excitation delay time is reduced. In this study, we used a combination of the partial element equivalent circuit method and the finite element method to perform a current distribution and thermal analysis of the behavior of NI REBCO coils when a local normal-state transition occurs. We also considered the appropriate turn-to-turn contact electrical resistance that could shorten the excitation delay time as much as possible while still suppressing the formation of hotspots, which is a disadvantage of the NI REBCO coil.
  • Kohei Nakazono, Hiroshi Ueda, Atsushi Ishiyama, So Noguchi, Hiroshi Miyazaki, Taizo Tosaka, Tsutomu Kurusu, Shunji Nomura, Shinichi Urayama, Hidenao Fukuyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 27 4 2017年06月 [査読有り][通常論文]
     
    In recent years, high-field magnets wound with RE-BCO tape and their applications to magnetic resonance imaging (MRI) have undergone considerable research and development. MRI coil systems require a highly accurate field in the imaging space. However, in REBCO coils, the irregular magnetic field generated by the screening current is induced by the radial component of the magnetic field in the REBCO tape, and may deteriorate the field quality both spatially and temporally. Therefore, a design process with consideration for the effect of the screening-current field is required for the reduction and correction of this field for a high-accuracy-field REBCO coil. In this study, the screening-current distribution in the REBCO tape and the irregular magnetic field were analyzed by using the simulation we developed for a REBCO model coil system for whole-body MRI. We additionally discuss the effect of the screening-current field in the REBCO coil based on the coil shape and arrangement to use it as feedback to the design stage.
  • So Noguchi, Vlatko Cingoski
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 27 4 2017年06月 [査読有り][通常論文]
     
    Second-generation high-temperature superconducting (HTS) tapes have been examined for applications, such as nuclear magnetic resonance, MRI, and accelerators. Each of these applications requires a precise magnetic field profile. However, screening currents induced while charging an HTS magnet degrade its magnetic field quality. Techniques to reduce the screening current effect have been proposed in the literature. One of the means to reduce screening currents is to apply an ac magnetic field using a "shaking magnet."The shaking effect enhances the quality of magnetic field by reallocating the screening currents inside HTS tapes. Although some experiments to study the shaking field effect were reported, the current distribution inside HTS tapes has not yet been clarified by simulation. This paper presents the simulation results for an ac magnetic field applied to a REBCO tape to reduce the influence of screening currents. In addition, we investigated the influence of the angle of applied ac magnetic field at the magnet center. The area of negative current density is also shown. From the simulation results, we conclude that a shaking field applied at an angle between 10 degrees and 30 degrees is effective to reduce the screening current effect.
  • Ryosuke Miyao, Hajime Igarashi, SeokBeom Kim, So Noguchi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 27 4 2017年06月 [査読有り][通常論文]
     
    Recently, multiple-stacked pancake coils wound with rare-earth barium copper oxide (REBCO) tapes are expected to apply for nuclear magnetic resonance (NMR)/MRI magnets. Since REBCO tapes are very expensive, REBCO magnets should be optimally designed so as to minimize the winding volume. Surely, a highly homogeneous magnetic field is also required for NMR/MRI magnets. To achieve the accurate homogeneity of REBCO magnets, it is necessary to compute the contribution of all REBCO layers one by one, because currents carry over very thin area compared with a whole magnet cross section. However, NMR/MRI magnets generating high-magnetic field usually consist of multiple-stacked REBCO pancake coils, and each pancake coil has > 300 turns. To evaluate the field homogeneity contributed by every REBCO layer, therefore, it is necessary to repeatedly compute more than ten thousand times as one magnet shape. In a conventional optimization algorithm, it is necessary to iterate more than one million times for the optimal design of an NMR or MRI magnet. Such an iterative computation is not realistic. Based on the backgrounds, we present a fast computation method using the shift operator of spherical harmonics. In addition, to confirm the validity of the proposed method, it was applied to the shape optimization of 1.5-T MRI magnet. In this paper, the optimization result and computation time are also shown.
  • So Noguchi, Takuto Naoe, Hajime Igarashi, Shinya Matsutomo, Vlatko Cingoski, Akira Ahagon, Akihisa Kameari
    IEEE TRANSACTIONS ON MAGNETICS 53 6 2017年06月 [査読有り][通常論文]
     
    Mesh quality strongly affects the solution accuracy in electromagnetic finite-element analysis. Hence, the realization of adequate mesh generation becomes a very important task. Several adaptive meshing methods for automatic adjustments of the mesh density in accordance with the shape and complexity of the analyzed problem have been proposed. However, the most of them are not enough robust, some are quite laborious and could not be universally used for adaptive meshing of complex analysis models. In this paper, a new adaptive mesh refinement method based on magnetic field conservation at the border between finite elements is proposed. The proposed error estimation method provides easy mesh refinements, and generates smaller element within regions with large curvature of the magnetic flux lines. The proposed adaptive mesh refinement method based on non-conforming edge finite elements, which could avoid generation of flat or ill-shaped elements, was applied to a simple magnetostatic permanent magnet model. To confirm the validity and accuracy, the obtained results were compared with those obtained by means of the Zienkiewicz-Zhu (ZZ) error estimator. The results show that the computational error using the proposed method was reduced down to 1% compared with that of the ZZ method, which yields error of 8.6%, for the same model.
  • Hiroshi Miyazaki, Sadanori Iwai, Yasumi Otani, Masahiko Takahashi, Taizo Tosaka, Kenji Tasaki, Shunji Nomura, Tsutomu Kurusu, Hiroshi Ueda, So Noguchi, Atsushi Ishiyama, Shinichi Urayama, Hidenao Fukuyama
    SUPERCONDUCTOR SCIENCE & TECHNOLOGY 29 10 2016年10月 [査読有り][通常論文]
     
    A project on the development of REBa2Cu3O7-delta (REBCO) magnets for ultra-high-field magnetic resonance imaging (MRI) was started in 2013. Since REBCO-coated conductors feature high mechanical strength under tensile stress and high critical current density, use of REBCO coils would allow superconducting magnets to be made smaller and lighter than conventional ones. In addition, a conduction-cooled superconducting magnet is simpler to use than one cooled by a liquid helium bath because the operation and maintenance of the cryogenic system become simpler, without the need to handle cryogenic fluid. Superconducting magnets for MRI require homogeneous, stable magnetic fields. The homogeneity of the magnetic field is highly dependent on the coil shape and position. Moreover, in REBCO magnets, the screening-current- induced magnetic field, which changes the magnetic field distribution of the magnet, is one of the critical issues. In order to evaluate the magnetic field homogeneity and the screening-current- induced magnetic field, a 1 T model magnet and some test coils were fabricated. From an evaluation of the 1 T model magnet, it was found that the main reason for magnetic field inhomogeneity was the tolerances in the z-axis positions of the coils, and therefore, it is important to control the gap between the single pancakes. In addition, we have already demonstrated the generation of an 8.27 T central magnetic field at 10 K with a small test coil. The screening-current-induced magnetic field was 0.43 T and was predictable by using an electromagnetic field simulation program. These results were reflected in the design of a conduction-cooled 9.4 T REBCO magnet for whole-body MRI systems. The magnet was composed of six main coils and two active shield coils. The total conductor length was 581 km, and the stored energy was 293 kJ. The field inhomogeneity was 24 ppm peak to peak and 3 ppm volume-root-mean-square (VRMS) for a 500 mm diameter spherical volume (DSV). The axial and radial 5 gauss line locations were less than 5 m and 4.2 m respectively.
  • S. Iwai, H. Miyazaki, Y. Ohtani, T. Tosaka, K. Tasaki, S. Nomura, T. Kurusu, H. Ueda, S. Noguchi, A. Ishiyama, S. Urayama, H. Fukuyama
    IEEE Transactions on Applied Superconductivity 26 4 2016年06月 [査読無し][通常論文]
     
    © 2002-2011 IEEE. A REBCO-coated conductor has a tape shape and is suitable for forming a stack of single pancakes for generating a high magnetic field. However, the magnetic flux going through the tape surface causes a screening current, which reduces the magnetic field in conventional coil designs. Magnetic resonance imaging systems need high uniformity of the magnetic field, both spatially and temporally, and thus, the screening field resulting from the screening current is one of the critical issues. In this paper, a 10-T class small test coil using REBCO-coated conductors was fabricated and tested in a conduction-cooled configuration from 10 to 60 K for investigating the effect of the screening field on the generated magnetic field in the inner space of the coil. The coil was composed of a stack of 22 single pancakes using 4-mm-wide REBCO tapes with an inner diameter of 50 mm, an outer diameter of 129 mm, and a height of 104 mm. For different stacking orders based on the coil critical currents, the measured values of the central magnetic field at 10 K were 7.66 and 8.27 T, which were lower than the calculated values of 8.07 and 8.70 T obtained without taking account of the screening-current fields.
  • S. B. Kim, R. Saito, M. Takahashi, Y. J. Park, M. H. Lee, Y. K. Oh, S. Noguchi
    IEEE Transactions on Applied Superconductivity 26 4 2016年06月 [査読無し][通常論文]
     
    © 2016 IEEE. The low temperature superconducting (LTS) coils are used in NMR devices, and liquid helium is used for their cooling. It is possible to reduce the operating costs by manufacturing the superconducting magnet that is consisted of the high temperature superconducting (HTS) coil using liquid nitrogen cooling. We have been developing the NMR relaxometry devices using the HTS double pancake coils and operated in the persistent current mode at liquid nitrogen temperature. The required strength and homogeneity of the magnetic field of proposed NMR relaxometry devices are 1.5 T and 150 ppm/cm3, respectively. To achieve the target field strength of 1.5 T, it is necessary to increase the numbers of pancake coils and winding turns of each coil, and the large operating current is required as much as possible. In this paper, Ic-B properties of HTS wire and superconducting joint are measured to determine the operating current (load line) for the proposed NMR relaxometry devices. Moreover, 3-D finite-element-model-based analysis was carried out to design the stacked HTS magnets for compact NMR relaxometry with downsizing and low cost.
  • Ayumu Mochida, Hiroshi Ueda, So Noguchi, Tao Wang, Atsushi Ishiyama, Hiroshi Miyazaki, Taizo Tosaka, Shunji Nomura, Tsutomu Kurusu, Shinichi Urayama, Hidenao Fukuyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 26 4 2016年06月 [査読有り][通常論文]
     
    Coil systems are fabricated with various combinations of multiple coils in order to generate homogenous fields for NMR and MRI applications. In multiple coil systems using REBCO coils, the behavior of the screening current, which deteriorates field homogeneity, depends on the patterns of the transport current, the charging sequence of the coils, and the various resulting magnetic fields. It is therefore important to investigate and clarify the behavior of the irregular magnetic field and screening current in multiple coil systems under different operating environments. In a previous study, we experimentally and numerically clarified the different behaviors of irregular magnetic fields based on the charging sequence of coils in multiple-model REBCO coils [1], [2]. In this paper, we constructed the multiple-model REBCO coils in order to obtain the fundamental data for reducing or improving the resulting irregular magnetic field. Furthermore, the distribution of the irregular magnetic field in terms of the screening current was measured by using the reversal current method [3], [4]. We also calculated the spatial and temporal behavior of the irregular magnetic field by using our developed 3-D numerical simulation. Based on the experimental and numerical results, we discuss the behavior of the magnetic field in terms of the screening current when using the current sweep reversal method in multiple-model REBCO coils.
  • Aika Ikeda, Takahiro Oki, Tao Wang, Atsushi Ishiyama, Katsutoshi Monma, So Noguchi, Tomonori Watanabe, Shigeo Nagaya
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 26 4 2016年06月 [査読有り][通常論文]
     
    Recently, no-insulation (NI) winding techniques have been proposed for achieving high current density and high thermal stability. To verify the excellent characteristics achieved using these techniques, we investigated the transient behaviors of NI REBCO pancake coils. In this paper, we evaluate transient electromagnetic and thermal behaviors during a local normal-state transition, based on a partial element equivalent circuit and thermal coupled numerical analysis. Moreover, we investigate temporal and spatial current distributions in the NI coil winding after a local normal transition occurs. We also clarify the reason for the suppression of temperature increase caused by the local normal-state transition in the NI winding. Subsequently, we evaluate the influence of the thickness of a Cu stabilizer on the thermal stability of the NI and conventional insulation windings. Finally, we discuss the mechanism of high thermal stability attained in the NI coil winding technique.
  • Taizo Tosaka, Hiroshi Miyazaki, Sadanori Iwai, Yasumi Otani, Masahiko Takahashi, Kenji Tasaki, Shunji Nomura, Tsutomu Kurusu, Hiroshi Ueda, So Noguchi, Atsushi Ishiyama, Shinichi Urayama, Hidenao Fukuyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 26 4 2016年06月 [査読有り][通常論文]
     
    An R&D project on high-temperature superconducting (HTS) magnets using (RE) Ba2Cu3O7 (REBCO; RE = rare earth) wires for ultrahigh-field (UHF) magnetic resonance imaging (MRI) systems is described. Our targets are 9.4-T MRI systems for whole-body imaging and brain imaging. REBCO wires are promising components for UHF-MRI because REBCO wires have high critical current density in high magnetic fields and high strength against hoop stresses, which allows MRI magnets to be smaller and lighter than conventional ones. The aim of the project is to establish basic magnet technologies for adapting REBCO coils for UHF-MRI. The project term is three years, and this year is the final year. We have already demonstrated the generation of an 8.27-T magnetic field with a small test coil composed of 22 REBCO pancake coils. A magnetic field spatial distribution with inhomogeneity of several hundreds of parts permillion within 100-mm diameter spherical volume (DSV) was demonstrated with a 1-T model magnet. A stable magnetic field of a few parts per million per hour was also demonstrated with the 1-T model magnet. The targets of the project, to be achieved by March 2016, are to demonstrate the generation of a 9.4-T field with the small REBCO coil, and to demonstrate a homogeneous magnetic field in 200-mm DSV with a 1.5-T magnet having three pairs of split coils. Imaging will be performed with the 1.5-T magnet.
  • So Noguchi, Katsutoshi Monma, Sadanori Iwai, Hiroshi Miyazaki, Taizo Tosaka, Shunji Nomura, Tsutomu Kurusu, Hiroshi Ueda, Atsushi Ishiyama, Shinichi Urayama, Hidenao Fukuyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 26 4 2016年06月 [査読有り][通常論文]
     
    It is important to investigate the stability and behavior of an epoxy-resin-impregnated no-insulation (NI) REBCO pancake coil to implement high-field applications, such as ultra-high-field magnetic resonance imaging. We have performed sudden discharging and overcurrent tests for the impregnated NI REBCO pancake coil. From the discharging test, the contact resistivity is estimated, and it changes depending on the initial current. From the overcurrent test, the high thermal stability of the impregnated NI REBCO pancake coil is confirmed. The REBCO pancake coil is charged up to 67 A though the critical current is only 46 A, and no degradation has been found. To investigate in detail the electromagnetic behavior of an impregnated NI REBCO pancake coil, the simulation is performed by means of the partial element equivalent circuit (PEEC) model. In the sudden discharging test, the simulation results for the case of lower initial current are in good agreement with the experimental data. As can be inferred from the simulation results, the current drastically decreases from the inside of the impregnated NI REBCO pancake coil. The result of the overcurrent simulation is almost identical to the experimental one. However, since the contact resistivity is presumed to be constant in the simulation, the difference is observed in the high current region.
  • Ayako Matsumi, Hiroshi Ueda, So Noguchi, Tao Wang, Atsushi Ishiyama, Hiroshi Miyazaki, Taizo Tosaka, Shunji Nomura, Tsutomu Kurusu, Shinichi Urayama, Hidenao Fukuyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 26 4 2016年06月 [査読有り][通常論文]
     
    In recent years, research and development of applications for a high field magnet wound with a REBCO tape into nuclear magnetic resonance and magnetic resonance imaging have been carried out. These applications require a very high accuracy field, that is, the spatial uniform and temporally stable field. However, in the REBCO coils, the irregular magnetic field is generated by the screening current, which is remarkably induced by the radial component of the magnetic field in a REBCO tape. Therefore, a nonconventional approach is required for the reduction or correction of the irregular magnetic field generated by the screening current in the stage of design for a high-accuracy-field REBCO coil. The prediction and improvement of the irregular magnetic field generated by the screening current is a serious issue for the development and design of REBCO coils and correction shims. In this study, we numerically investigated the screening current distribution in the winding and the irregular magnetic field generated by the screening current. Moreover, we discuss the irregular effect of the magnetic field generated by the screening current in the REBCO coil from the arrangement of the coil windings and excitation pattern.
  • Hiroshi Ueda, Yohei Imaichi, Tao Wang, Atsushi Ishiyama, So Noguchi, Sadanori Iwai, Hiroshi Miyazaki, Taizo Tosaka, Shunji Nomura, Tsutomu Kurusu, Shinichi Urayama, Hidenao Fukuyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 26 4 2016年06月 [査読有り][通常論文]
     
    In a REBCO superconducting magnet for magnetic resonance imaging (MRI) applications, the large screening current induced by a magnetic field perpendicular to the winding tape is a serious problem: it generates irregular magnetic field that deteriorates the spatial field homogeneity and temporal field stability in MRI applications. Therefore, we need to estimate the magnetic field generated by the screening current using electromagnetic field analysis to design and develop a REBCO magnet that generates highly accurate and stable magnetic field. Therefore, to examine the influence of the magnetic field generated by the screening current, we constructed cryocooler-cooled small bore-coil stacked pancake REBCO coils with an inner diameter of 50 mm. This coil generates a magnetic field of 10 T at the center. In this study, we report the evaluation of the current distribution and magnetic field in the REBCO coil using the developed 3-D numerical simulation code for electromagnetic field analysis in a REBCO tape using the finite-element method and fast multipole method. The numerical results agree well with the experimental results. Furthermore, we discuss the current distribution in the REBCO tape and the spatial and temporal behavior of the magnetic field on the basis of the results of the experiments and numerical simulation.
  • Takahiro Oki, Aika Ikeda, Tao Wang, Atsushi Ishiyama, So Noguchi, Katsutoshi Monma, Tomonori Watanabe, Shigeo Nagaya
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 26 4 2016年06月 [査読有り][通常論文]
     
    We have been developing a no-insulation (NI) winding technique to be used in both high thermal stability and high current density, which have a tradeoff relationship. This paper presents numerical and experimental studies on the thermal stability of an NI REBCO pancake coil by focusing on a quench protection scheme. In the case of an accident or a local normal-state transition, the power supply for the superconducting coil must be immediately shut down in order to ensure its safety. During the sudden discharging of a conventional insulated winding coil, most of the stored electromagnetic energy is dissipated by an external dump resistor connected across the coil terminals as a quench protection system. However, in an NI pancake coil, current flows in the radial direction in order to bypass the local normal-state area to the adjacent turns. The stored energy in the coil may be dissipated as Joule heat owing to the turn-to-turn contact electrical resistance. In this study, by using experiments and numerical analyses, we evaluated two transient behaviors during sudden discharging: the distribution of energy dissipation and the temperature increase in model NI REBCO pancake coils. We also evaluated the thermal behavior of the NI coil during a local normal transition.
  • H. Miyazaki, S. Iwai, Y. Otani, M. Takahashi, T. Tosaka, K. Tasaki, S. Nomura, T. Kurusu, H. Ueda, S. Noguchi, A. Ishiyama, S. Urayama, H. Fukuyama
    IEEE Transactions on Applied Superconductivity 26 3 2016年04月 [査読無し][通常論文]
     
    © 2002-2011 IEEE. Development of a higherature superconducting magnet wound with REBa2Cu3O7-δ (REBCO)-coated conductor for ultrahigh-field magnetic resonance imaging (MRI) is in progress. Our final targets are 9.4-T MRI systems for whole-body and brain imaging. Since REBCO-coated conductors feature high mechanical strength under a tensile stress and high critical current density, superconducting magnets could be made smaller by using REBCO coils. Superconducting magnets for MRI require homogeneous stable magnetic fields. The homogeneity of the magnetic field is highly dependent on the size and current density of the coils. Furthermore, in REBCO magnets, the screening-current-induced magnetic field that changes the magnetic field distribution of the magnet is one of the critical issues. In order to evaluate the magnetic field homogeneity and the screening-current-induced magnetic field of REBCO magnets, a conduction-cooled REBCO magnet with a roomerature bore of 200 mm was fabricated and tested. The REBCO coils were composed of 12 single pancakes, and the size of the homogeneous magnetic field region was 100-mm diameter spherical volume (DSV). The central magnetic field was as high as 1 T at 285 A. The magnetic field distribution on the z-axis was measured by using an NMR probe. The maximum error magnetic field was 470 parts per million (ppm) in the range from -50 to +50 mm, as well as in the coefficients of the spherical harmonic expansion for a 100-mm DSV. The error magnetic fields due to the screening-current-induced magnetic field were less than 5 ppm, because there was a sufficient distance between the coil and the homogeneous magnetic field region. The main reason for the error magnetic field was dimensional errors in the outer diameters and positions on the $z$-axis.
  • So Noguchi, Katsutoshi Monma, Hajime Igarashi, Atsushi Ishiyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 26 3 2016年04月 [査読有り][通常論文]
     
    The no-insulation (NI) winding technique for an NI ReBCO pancake coil is expected to improve dynamic and thermal stability and enhance current density. The investigations on electromagnetic and thermal behaviors are important for the development of NI ReBCO coils. Many stability investigations of the NI ReBCO coil itself have been carried out by experiments and simulations. However, the detailed behavior of the bypass current between turns has not been shown. Although contact resistivity was obtained through prior experiment, it included the resistivity of not only contact surface but also the components, i.e., the copper stabilizer and the Hastelloy substrate, of a ReBCO tape. To investigate the detailed bypass current behavior in this paper, the true contact surface resistivity is taken into account in the simulation. The bypass current on the cross section of the NI ReBCO tape is simulated using the two-dimensional finite-element method. From the simulation results, the influence of the coil-radial resistivity between turns on the turn-to-turn contact surface resistivity is clarified. In addition, the heat loss is also reported, and a simple equivalent circuit of the turn-to-turn contact is proposed.
  • Takuto Naoe, So Noguchi, Vlatko Cingoski, Hajime Igarashi
    IEEE TRANSACTIONS ON MAGNETICS 52 3 2016年03月 [査読有り][通常論文]
     
    The visualization of magnetic flux lines is one of the most effective ways to intuitively grasp a magnetic field. The depiction of continuous and smooth magnetic flux lines according to the magnetic field is of paramount importance. Thus, it is important to adequately allocate the distribution of magnetic flux lines in the analyzed space. We have already proposed two methods of determining the allocation of magnetic flux lines in 3-D space. However, both the methods exhibited a long computation time to determine the allocation of magnetic flux lines. For solving this problem, in this paper, we propose a new improved method for the correct allocation of magnetic flux lines in the 3-D space with modest computational cost. The main advantages of this method are shorter computation time, correct allocation of the magnetic flux lines, and, especially, short computation time for the visualization of magnetic flux lines when changes in the number of depicted flux lines are requested.
  • Taizo Tosaka, Hiroshi Miyazaki, Sadanori Iwai, Yasumi Otani, Masahiko Takahashi, Kenji Tasaki, Shunji Nomura, Tsutomu Kurusu, Hiroshi Ueda, So Noguchi, Atsushi Ishiyama, Shinichi Urayama, Hidenao Fukuyama
    PROCEEDINGS OF THE 28TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS 2015) 81 145 - 148 2016年 [査読有り][通常論文]
     
    An R&D project on high-temperature superconducting (HTS) magnets using rare-earth Ba2Cu3O7 (REBCO) wires was started in 2013. The project objective is to investigate the feasibility of adapting REBCO magnets to ultrahigh field (UHF) magnetic resonance imaging (MRI) systems. REBCO wires are promising components for UHF-MRI magnets because of their superior superconducting and mechanical properties, which make them smaller and lighter than conventional ones. Moreover, REBCO magnets can be cooled by the conduction-cooling method, making liquid helium unnecessary. In the past two years, some test coils and model magnets have been fabricated and tested. This year is the final year of the project. The goals of the project are: (1) to generate a 9.4 T magnetic field with a small test coil, (2) to generate a homogeneous magnetic field in a 200 mm diameter spherical volume with a 1.5 T model magnet, and (3) to perform imaging with the 1.5 T model magnet. In this paper, the progress of this R&D is described. The knowledge gained through these R&D results will be reflected in the design of 9.4 T MRI magnets for brain and whole body imaging. (C) 2016 Published by Elsevier B.V.
  • So Noguchi, Ryosuke Miyao, Hajime Igarashi, Atsushi Ishiyama
    2016 IEEE CONFERENCE ON ELECTROMAGNETIC FIELD COMPUTATION (CEFC) 2016年 [査読有り][通常論文]
     
    When designing an MRI magnet, its field homogeneity is evaluated by higher-order coefficients of the Legendre polynomial expression than 0th. Recently, the development of ultra-high-field (similar to 10 T) MRI magnet wound with REBCO tapes is underway. REBCO tapes are flat, and its current-carrying region is very narrow compared to its cross section. However, to compute the higher-order coefficients for MRI REBCO magnet is a labor task because the currentcarrying region is discretely arranged.In this paper, we propose an accelerated method of computing the higher-order coefficients of the Legendre polynomials for MRI REBCO magnet design using a shift operator.
  • Yoshihiko Sugihara, Toshifumi Honda, Yuta Urano, Masahiro Watanabe, So Noguchi, Hajime Igarashi
    ELECTRONICS AND COMMUNICATIONS IN JAPAN 98 6 36 - 43 2015年06月 [査読有り][通常論文]
     
    Usually, wafer inspection is a two-step process. The first step, which is very important, consists of detection of defects on the wafer. The second step classification of the detected defects, which is done after defect detection as necessary. Recently, it has become necessary to perform simultaneous detection and classification of wafer defects in order to reduce the wafer inspection time while maintaining high resolution of inspection. Optical wafer inspection is the most effective method for detecting and classifying defects and estimating their size in a short time. In this method, the scattered light distribution is compared with a database of previous scattered light distributions and pattern matching is used to classify defects and estimate their size. Therefore, to achieve optical wafer inspection based on scattered light distribution, it is necessary to gather scattered light distribution data for many samples of various kinds. The first aim of this study is to develop a defect classification and size estimation method utilizing the scattered light distribution. We propose a method of classifying defects on wafers and estimating their size. The proposed method is based on pattern matching utilizing a parametric eigenspace. The second aim of the paper is to validate the proposed method by applying it to scattered light distribution samples. The light scattering distribution samples were generated by discrete dipole approximation (DDA) simulation. A database of the light scattering distribution is easily created using the simulation. (C) 2015 Wiley Periodicals, Inc.
  • Xudong Wang, Tao Wang, Erika Nakada, Atsushi Ishiyama, Ryusei Itoh, So Noguchi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 25 3 4601805,1-5  2015年06月 [査読有り][通常論文]
     
    This paper presents analytical studies on the charging characteristics of a no-insulation (NI) REBCO pancake coil. A partial element equivalent circuit (PEEC) model has been developed to evaluate the local current paths in NI REBCO pancake coils. The PEEC model is able to consider the asymmetry of the coil winding, the partial turn-to-turn contact electrical resistance, and the partial self and mutual inductances. The analysis results are compared with previous charging experimental results and simulations using a simplified parallel equivalent circuit (SPEC) model to validate the proposed approach with the PEEC model. To investigate the charging characteristics of a meter-class NI REBCO pancake coil, numerical simulations were performed by using the PEEC and SPEC models as a parameter of the turn-toturn contact electrical resistance. In addition, the magnetic field in a 3-T NI REBCO coil was calculated by the SPEC model to clarify the charging delay of a practical scale magnet.
  • Tao Wang, So Noguchi, Xudong Wang, Issei Arakawa, Katsuhiko Minami, Katsutoshi Monma, Atsushi Ishiyama, Seungyong Hahn, Yukikazu Iwasa
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 25 3 4303409,1-9  2015年06月 [査読有り][通常論文]
     
    Stability margin of a high-temperature superconducting (HTS) coil is two or three orders of magnitude greater than that of a low-temperature superconducting coil. In recent years, many papers have reported test results of turn-to-turn no-insulation (NI) HTS coils having extremely enhanced thermal stability, such that burnout never occurs in an NI coil, even at an operating current exceeding 2.5 times the critical current. Thus, The main goal of this paper is to clarify transient electromagnetic and thermal behaviors and mechanism of the high thermal stability in an NI REBCO coil. A partial element equivalent circuit (PEEC) model is proposed for the numerical simulation of an NI REBCO coil, which considers a local electrical contact resistance between turns, an I-V characteristic of an REBCO tape, and local self and mutual inductances of the NI REBCO coil. Using the PEEC model, we investigate the influence of the turn-to-turn contact resistance on the transient behavior of the NI REBCO coil during sudden discharging. We also perform thermal conduction analyses with the PEEC model to clarify the transient behavior of an NI REBCO coil during an overcurrent operation.
  • So Noguchi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 25 3 4300405,1-5  2015年06月 [査読有り][通常論文]
     
    Magnets creating highly homogeneous and high magnetic field have been used in MRI, NMR, accelerator, and so on. Coils have various shapes, such as solenoid, dipole, D-shape, toroid. When employing a high-field superconducting magnet, it is hard to use ferromagnetic material for shimming because of its magnetic saturation. Commonly, a superconducting magnet is shimmed with currents, called "active shimming." Usually, for shimming, a magnetic field is expressed with spherical harmonics function. To achieve a highly homogeneous field, the higher order spherical harmonic coefficients than the 0th are vanished by suitably arranging shim coils. So far, a formulation of spherical harmonic expression of a circular coil is presented in many papers. However, the circular coil is restricted to eliminate inhomogeneity coefficients. Moreover, only the axial component of the spherical harmonics is represented in these papers. Recently, a few magnets are under development to create a magnetic field tilted from the axis. It is, therefore, necessary to vanish the inhomogeneous field of the entire components. This paper presents the spherical harmonic expression of the entire field components for an ellipsoidal coil, and the translation and rotation of spherical harmonics. Finally, an example of active shimming is shown.
  • John Voccio, Seungyong Hahn, Youngjae Kim, Jungbin Song, Kazuhiro Kajikawa, So Noguchi, Juan Bascunan, Yukikazu Iwasa
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 25 3 4301005,1-5  2015年06月 [査読有り][通常論文]
     
    We present results of full-current testing at 4.2 K of a z-axis 0.866-T solenoid and an x-axis 1.225-T dipole coil that comprise a 1.5-T/75-mm room temperature bore magic-anglespinning nuclear magnetic resonance magnet developed at the MIT Francis Bitter Magnet Laboratory. Also included in the paper are results of the magnet performance when the magnet assembly is immersed, to enhance its thermal mass, in solid nitrogen, and operated in the temperature range of 4.2-4.3 K.
  • So Noguchi, Shinya Matsutomo
    IEEE TRANSACTIONS ON MAGNETICS 51 3 7202904,1-4  2015年03月 [査読有り][通常論文]
     
    In this paper, we propose an economically efficient optimal design method of different-size interior permanent magnet (IPM) motors to maximize their efficiency. Since the homothetic shape is used, the optimization design is, at once, performed. The use of the commonalized design can reduce the productive costs. Game theory is employed as an optimization method. The game theory can simultaneously increase the efficiency of all the IPM motors with the common and homothetic shape. So far, there are no previous reports considering both the economical efficiency and the motor performance simultaneously. Therefore, the proposed optimal design method of the commonalized different-size IPM motors using the game theory method achieves a high electrical efficiency in addition to the economical efficiency due to design optimization.
  • Naoya Terauchi, So Noguchi, Hajime Igarashi
    IEEE TRANSACTIONS ON MAGNETICS 51 3 7202804,1-4  2015年03月 [査読有り][通常論文]
     
    High-temperature superconducting quantum interference devices (HTS SQUIDs) have been developed as an extremely sensitive magnetic sensor. The HTS SQUIDs are required to have high robustness with respect to the magnetic noise for stable operation in an unshielded environment and also reduced cost to widen the application range. It is, therefore, necessary to clarify the quantum magnetic behavior of the HTS SQUID. However, a simulation tool, which can consider the quantum magnetic behavior, has not been developed yet. In this paper, an equivalent circuit of a Josephson junction comprising the HTS SQUID is more properly considered to represent the quantum behavior. It can consider the ac and dc Josephson effect. The obtained results are compared with an ordinary simulation using a simplified circuit model, and the results agree well with each other. Using the proposed simulation method instead of the ordinary simulation, the current path is more accurately simulated, so this new method will be used to evaluate the robustness of the SQUID.
  • Taizo Tosaka, Hiroshi Miyazaki, Sadanori Iwai, Yasumi Otani, Masahiko Takahashi, Kenji Tasaki, Shunji Nomura, Tsutomu Kurusu, Hiroshi Ueda, So Noguchi, Atsushi Ishiyama, Shinichi Urayama, Hidenao Fukuyama
    PROCEEDINGS OF THE 27TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS 2014) 65 217 - 220 2015年 [査読有り][通常論文]
     
    A project to develop an ultra-high-field magnetic resonance imaging (MRI) system based on HTS magnets using (RE)Ba2Cu3O7 (REBCO; RE=rear earth) coils is underway. The project is supported by the Japanese Ministry of Economy, Trade and Industry and aims to establish magnet technologies for a whole-body 9.4 T MRI system. REBCO wires have high critical current density in high magnetic fields and high strength against hoop stresses, and therefore, MRI magnets using REBCO coils are expected to have cryogenic systems that are smaller, lighter, and simpler than the conventional ones. A major problem in using REBCO coils for MRI magnets is the huge irregular magnetic field generated by the screening current in REBCO tapes. Thus, the main purpose of this project is to make the influence of this screening current predictable and controllable. Fundamental technologies, including treatment of the screening currents, were studied via experiments and numerical simulations using small coils. Two types of model magnets are planned to be manufactured, and the knowledge gained in the development of the model magnets will be reflected in the magnet design of a whole-body 9.4 T MRI system. (C) 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
  • So Noguchi, Katsutoshi Monma, Ryusei Itoh, Hajime Igarashi
    PROCEEDINGS OF THE 27TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS 2014) 65 233 - 236 2015年 [査読有り][通常論文]
     
    The no-insulation winding technique is a promising way of enhancing the thermal stability of NbTi superconducting coils. However, it takes a long time to charge a no-insulation superconducting coil, because the time constant is relatively large. Hence, a partial-insulation winding technique was also proposed to reduce the time constant with a high thermal stability. However, the time constant of the previously proposed partial-insulation NbTi superconducting coil could not drastically be improved, and the cause was investigated using a partial-element equivalent circuit model. Therefore, in this paper, we propose a new partial-insulation structure, and the effectiveness is verified using a partial element equivalent circuit model. The results show that a relatively small time constant is achieved when charging and discharging the proposed partial-insulation NbTi superconducting coil. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
  • So Noguchi, Ryusei Itoh, Yuki Oga, Hajime Igarashi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 24 3 5700304,1-4  2014年06月 [査読有り][通常論文]
     
    Recently, many investigations about toroidal high-temperature superconducting magnetic energy storage systems have been reported. Some papers reported that there was a possibility that the chain of normal-state transitions occurred on the toroidal HTS-SMES magnet by normal-state-transition simulation. Hence, it should also be investigated that the behavior of unbalanced electromagnetic force during the sequential normal-state transition of the superconducting coil elements. In this paper, we have developed a simulation code to investigate the behavior of the overturning electromagnetic force on the toroidal HTS-SMES system during the normal-state transition. The magnetic field and the circuit analysis were coupled and solved in the previously developed simulation code. Additionally, in order to investigate the normal-state transition more accurately, we also take the thermal analysis into account. Carrying out the newly developed numerical simulation, we investigate the time transition of the transport current, the overturning force, and the magnetic field applied to the superconducting coil elements for a few toroidal HTS-SMESs.
  • So Noguchi, Ryusei Itoh, Seungyong Hahn, Yukikazu Iwasa
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 24 3 4900504,1-4  2014年06月 [査読有り][通常論文]
     
    A no-insulation winding technique for an NbTi superconducting coil is expected to improve its dynamic stability during charging or discharging. Experimental results, recently reported, demonstrated the charging stability enhancement of an NI coil. In an NI winding, an amount of current can bypass to adjacent wires to avoid the generation of a local hot spot and, as a result, the dynamic stability is improved. In spite of the potential technical merits of the NI technique, the charging responses of an NI coil, including the non-uniform current distribution under a time-varying condition, have not been investigated analytically yet. In this paper, we propose a simulation method using an equivalent circuit equation for an NI coil with its inductance and the contact turn-to-turn resistances taken into consideration. The simulation results were analyzed in three aspects: terminal voltage, loss energy, and stored magnetic energy.
  • Hiroshi Ueda, Mitsuhiro Fukuda, Kichiji Hatanaka, Kenta Michitsuji, Hiraku Karino, Tao Wang, Xudong Wang, Atsushi Ishiyama, So Noguchi, Yoshinori Yanagisawa, Hideaki Maeda
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 24 3 4701505,1-5  2014年06月 [査読有り][通常論文]
     
    In coils wound with high-temperature superconducting (HTS) tapes, large screening currents are induced in the tape by the radial component of the magnetic field. Furthermore, when a transport current is supplied to the HTS tape under a magnetic field, the total current (which consists of the transport and screening currents) flows inhomogeneously. The magnetic field generated by the screening currents affects the magnetic field distribution in cyclotron applications. Investigating the effects of the screening currents on the reduction, hysteresis, and drift of the magnetic field in the HTS coil is therefore necessary. In our previous studies, we have developed a novel simulation code for a three-dimensional electromagnetic field with the aim of clarifying these effects. In the present study, we measured the reduction and hysteresis of the magnetic field generated by the screening currents for a small model of HTS pancake coil. Additionally, we numerically investigated the influence of the screening current in the Furs coil on the spatial and temporal behavior of the magnetic field using our developed simulation code, which considers the nonlinear voltage-current characteristics.
  • So Noguchi, Seungyong Hahn, Yukikazu Iwasa
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 24 3 4400904,1-4  2014年06月 [査読有り][通常論文]
     
    The superconducting dipole magnets wound with HTS wires have been developed for a magic-angle-spinning NMR. The magnetic field of the dipole magnets is tilted from z-axis. Since the highly homogeneous magnetic field is required, the magnetic field of the dipole magnets is necessarily compensated by passive and/or active shimming. However, the compensation of all the components has not been reported. Usually, due to the axial symmetry of a solenoid magnet, only z component of the magnetic field is homogenized. In this paper, all the x, y, and z components of the magnetic field generated by the superconducitng dipole magnet are compensated because of the tilt from the z-axis.
  • So Noguchi
    JOURNAL OF APPLIED PHYSICS 115 16 163908-163908-18  2014年04月 [査読有り][通常論文]
     
    For MRI and NMR magnet design, a highly homogeneous and high magnetic field has to be achieved by active and/or passive shimming. The active and passive shimming commonly homogenize the magnetic field around the magnet center by cancellation of the higher terms of a spherical harmonic series than the 0th term. So far, the spherical harmonic expression in the cylindrical coordinate system is well known for a circular coil, a solenoid coil, and magnetization of ferromagnetic material with/without its volume. In a shimming design, only the z-component of an inhomogeneous magnetic field is compensated because it is dominant to the performance of MRI/NMR. However, various kinds of MRI and NMR systems have recently been developed, and these magnets sometimes have an axially asymmetric configuration or generate a tilted magnetic field. Therefore, the entire x-, y-, and z-components have to be homogenized for such magnets. I derive the spherical harmonic expression of the entire components of magnetic field generated by a circular coil, a dipole coil, and a straight line current. In addition, since the entire magnetization components of the ferromagnetic material having the volume contribute the entire components of the magnetic field around the magnet center, I also derive the equations of the spherical harmonic coefficients of the magnetic field generated by ferromagnetic material. Since these equations need a numerical integration, such as the Gauss quadrature integration, the computation accuracy of the spherical harmonic coefficients is investigated against the number of the evaluation points. We can calculate the highly accurate spherical harmonic coefficients with the small number of the evaluation points. (C) 2014 AIP Publishing LLC.
  • So Noguchi, Tomoyuki Miyamoto, Shinya Matsutomo
    IEEE TRANSACTIONS ON MAGNETICS 50 2 7016004,1-4  2014年02月 [査読有り][通常論文]
     
    The optimization method is often used for designing the configuration of electromagnetic apparatuses in order to enhance performance. Many optimal design methods have been developed and popularized. However, most of the optimal design methods can only take into account a single objective function. Therefore, when the problem has a few purposes, a weighted summed objective function is usually employed. Recently, we have proposed a new method, taking into account the multiple purposes simultaneously and individually. The proposed method can select one rational solution from among the Pareto optima, based on the game theory. However, the meaning of the selected rational solution is unclear. Therefore, the meaning is investigated by calculating the weight parameters of the weighted summed objective function so that the optimal solution of the weighted summed objective function is identical to the rational solution of the game theory. We can intuit the meaning of the rational solution by comparing the weight parameters.
  • So Noguchi, SeokBeom Kim, Seungyong Hahn, Yukikazu Iwasa
    IEEE TRANSACTIONS ON MAGNETICS 50 2 7014904,1-4  2014年02月 [査読有り][通常論文]
     
    When a magnet generating highly homogeneous magnetic field is designed, a shimming is required. The shimming is usually performed so that the magnetic field only in the axis direction is compensated by iron pieces and/or coils. The compensation is commonly achieved by eliminating the coefficients of the spherical harmonics expansion of the magnetic field generated by the main magnet. Some papers showed the coefficients of the spherical harmonics expansion in only the z-direction for passive shimming. However, recently some magnets generate a magnetic field tilted from the z-axis, such as a magic-angle-spinning nuclear magnetic resonance/MRI. It is, therefore, necessary to eliminate the coefficients of the spherical harmonics expansion in the x- and y-direction.
  • So Noguchi, Fumiaki Nobuyama, Hajime Igarashi
    IEEE TRANSACTIONS ON MAGNETICS 50 2 701104,1-4  2014年02月 [査読有り][通常論文]
     
    An automatic mesh generation method employing a dynamic bubble system can provide a high-quality mesh for electromagnetic finite element analysis. However, it takes a very long time to compute bubbles' movement when a mesh with a large number of elements is generated. The bubbles move according to a force among them, such as the van der Waals force. However, the force received from bubbles of very far distance can be ignored. Therefore, it is unnecessary to calculate the force from all the bubbles. In this paper, we propose a subdivided dynamic bubble system in order to shorten the computation time. The proposed method considers the analysis region to be divided into some tetrahedral subdivisions, and then the bubbles move independently in the tetrahedral subdivisions. As a result, acceleration of the computation time is achieved.
  • Naoya Terauchi, So Noguchi, Hajime Igarashi
    PROCEEDINGS OF THE 26TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS 2013) 58 200 - 203 2014年 [査読有り][通常論文]
     
    A SQUID is a highly sensitive magnetic sensor. However, a defect of SQUID is high susceptibility to magnetic noise. The high robustness of SQUID with respect to magnetic noise enables to widen the range of applications. We have striven to clarify the mechanism of weakness in magnetic noise by means of numerical electromagnetic field simulation to support a SQUID development. However, a Josephson junction was modeled as a constant resistance and a SQUID behaviour was not correctly simulated in the previous paper. Therefore, the non-linear current-voltage characteristic of the Josephson junction is newly taken into account the simulation to represent the SQUID behaviour. As the results, the phenomena of the step-increasing magnetic flux and the spike voltage that could not be reproduced in the previous paper is simulated. It is successful to qualitatively evaluate the SQUID behaviour, i.e. it becomes possible to represent superconducting-to-voltage and voltage-to-superconducting state transitions. (C) 2014 The Authors. Published by Elsevier B.V.
  • Hiroshi Ueda, Mitsuhiro Fukuda, Kichiji Hatanaka, Tao Wang, Xudong Wang, Atsushi Ishiyama, So Noguchi, Shigeo Nagaya, Naoji Kashima, Nobuyuki Miyahara
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 23 3 4100205,1-5  2013年06月 [査読有り][通常論文]
     
    In recent years, the quality of high-temperature superconducting (HTS) tapes has been improving rapidly, becoming available in sufficient quantity and length, and can be applied to devices for power systems and industrial applications. Therefore, we are carrying out a feasibility study on the application of HTS coil to a medical accelerator system for particle cancer therapy, and designing a new HTS cyclotron that is to be compact, highly efficient, is able to extract high-energy beam and consume less power. In this paper, we report our effort to develop a conceptual magnetic design of a "next generation HTS cyclotron" using high-temperature superconducting technology.
  • Ryusei Itoh, Yuki Oga, So Noguchi, Hajime Igarashi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 23 3 4600905,1-5  2013年06月 [査読有り][通常論文]
     
    It was reported that a magnetic field perpendicular to a high temperature superconducting (HTS) tape induced a screening current in the HTS tape of an HTS magnet, and a central magnetic field decreased due to the screening current after the HTS magnet was charged. Hence, it is necessary to investigate the distribution of the screening current inside the HTS tape. This paper reports numerical simulation results about the current distribution and an electrical resistance inside the HTS tape of two HTS magnets, which have different shapes but generate the same central magnetic field, using the finite element method taking into account the E-J characteristic of the HTS tape. The results indicate that the distribution of the perpendicular magnetic field and the electrical resistivity are dependent on the coil shape. The current path in the HTS tape is determined from their distribution. It is concluded that the HTS magnet with a bad shape generates a little large electrical resistance.
  • Hiroshi Ueda, Mitsuhiro Fukuda, Kichiji Hatanaka, Tao Wang, Atsushi Ishiyama, So Noguchi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 23 3 4100805,1-5  2013年06月 [査読有り][通常論文]
     
    We intend to develop and obtain a compact, high-efficiency and high-performance cyclotron using the high-temperature superconducting (HTS) magnet technology. In cyclotron applications, a high-accuracy magnetic field distribution with an isochronous field and an azimuthally varying field is spatially and temporally required for an HTS coil. In coils wound with HTS tapes, large shielding currents are induced in the HTS tape by the radial component of the magnetic field. The magnetic field generated by the shielding current affects the magnetic field distribution in the cyclotron application in the following issues: (1) field reduction by the shielding current, (2) accuracy of the field distribution, (3) temporal stability of the time-dependent shielding currents, and (4) field repeatability after charge and discharge repetitions. These effects are very critical in cyclotron applications. We developed a novel numerical simulation based on the finite element method, boundary integral equation, and fast multipole method. We investigated the spatial and temporal behavior of the magnetic field attributed to the shielding current in the HTS coil for the HTS cyclotron application.
  • Yuki Oga, So Noguchi, Makoto Tsuda
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 23 3 5700204,1-4  2013年06月 [査読有り][通常論文]
     
    This paper describes a comparison of an optimal configuration of SMES magnets wound with MgB2 or YBCO conductors. For YBCO SMES, it is well known that a toroidal magnet is an ideal structure from the view point of the influence of the perpendicular component of magnetic field applied to an YBCO tape. We investigated an ideal structure for MgB2 SMES by comparing with the YBCO SMES. Because an MgB2 wire has no anisotropic magnetic property like an YBCO tape, the toroidal structure is unsuitable for MgB2 SMES. Therefore, we proposed a new structure of MgB2 SMES where the magnetic flux leaking between conductors is avoided. An MgB2 SMES of the proposed structure can store approximately 5.6 times higher than that of a single solenoid structure with the same winding volume.
  • Yuki Oga, So Noguchi, Hajime Igarashi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 23 3 4700505,1-5  2013年06月 [査読有り][通常論文]
     
    We previously investigated the stability of toroidal HTS-SMES magnets by simulation. The simulation took an electric circuit and a magnetic field phenomenon into account. However, a thermal condition is an important factor in investigating the behavior of an HTS-SMES magnet. Therefore, we have improved the previously developed simulation code to consider the thermal phenomenon. With the newly developed numerical simulation, we have investigated a time transition of a coil current, a critical current, and a temperature in the toroidal HTS-SMES magnets. As a result, it was confirmed that the temperature of all the HTS coils rose up quickly one after another, after the temperature at a certain local area of one HTS coil was increased.
  • So Noguchi, Atsushi Takada, Fumiaki Nobuyama, Masahiko Miwa, Hajime Igarashi
    IEEE TRANSACTIONS ON MAGNETICS 49 5 1705 - 1708 2013年05月 [査読有り][通常論文]
     
    A common mesh smoothing method strives to improve the shape quality of all elements. Generally a mesh consisting of only well-shaped elements is desired in finite element analysis. Although a perfect-shaped element yields short computation time, even a well-shaped element, whose shape is close to a regular polygon, sometimes prolongs the computation time of solving the system of equations derived with the edge-based finite element method. In this paper, we propose a new smoothing scheme of improving a convergence property of the system of equations by applying a common mesh smoothing method to some elements, which cause long computation time of the iterative solver. The proposed smoothing scheme utilizes the condition number of submatrices, into which coefficient matrix derived with the edge-based finite element method is subdivided, in order to choose ill-conditioned elements to be smoothed. As a result, the computation time is shortened applying a smoothing process only to the chosen ill-conditioned elements.
  • Fumiaki Nobuyama, So Noguchi, Hajime Igarashi
    IEEE TRANSACTIONS ON MAGNETICS 49 5 1677 - 1680 2013年05月 [査読有り][通常論文]
     
    An automatic mesh generation method employing a dynamic bubble system can provide a high-quality mesh for electromagnetic finite-element analysis. However, there is a problem in that it takes a very long time to compute the bubbles' movement when a mesh with a large number of elements is produced. It is possible to independently and simultaneously compute the bubbles' movement; therefore, the computation of the bubbles' movement is suitable for parallel computing. In order to shorten the computation time, the computation of the bubbles' movement is parallelized with the graphics-processing unit (GPU). We propose a dynamic bubble system parallelized with GPU. As a result, a reduction in computation time was achieved.
  • Shinya Matsutomo, Kenta Mitsufuji, Yuta Hiasa, So Noguchi
    IEEE TRANSACTIONS ON MAGNETICS 49 5 1665 - 1668 2013年05月 [査読有り][通常論文]
     
    In this paper, we propose a real-time visualization system utilizing Augmented Reality Technology for electromagnetics education. It gives an image of magnetic field generated by a bar magnet with a piece of iron in real-time, however the bar magnet and the piece of iron are represented by mock ones. In the newly proposed visualization system, these mocks are captured by a web camera, and mesh needed in the calculation of magnetic field is deformed. Subsequently, a finite element analysis is carried out in very short time and then the magnetic field is immediately visualized. Thereby, it is, in real-time, observable that magnetic flux lines generated by the bar magnet are attracted to a piece of iron. Moreover, when a user moves the mocks, the magnetic flux lines are immediately depicted according to the position of the mocks.
  • Tomoyuki Miyamoto, Shinya Matsutomo, Naoya Terauchi, So Noguchi, Hajime Igarashi
    INTERNATIONAL JOURNAL OF APPLIED ELECTROMAGNETICS AND MECHANICS 43 1-2 3 - 11 2013年 [査読有り][通常論文]
     
    Usually, multiple objectives have to be considered when an electromagnetic apparatus is optimally designed. In such a multipurposed optimal design problem many solutions exist and are termed Pareto optimum. Hence, we have previously proposed a multipurposed optimal design method based on a game theory. The proposed method can choose one rational solution from Pareto optima. It is, however, unconfirmed what the signification of the chosen rational solution is. Therefore, the signification is investigated by calculating the weight parameters of a weighted summed objective function.
  • 杉原 慶彦, 本田 敏文, 浦野 雄太, 渡辺 正浩, 野口 聡, 五十嵐 一
    電気学会論文誌C(電子・情報・システム部門誌) 133 11 15 - 2124 一般社団法人 電気学会 2013年 [査読無し][通常論文]
     
    Usually, there are two processes in wafer inspection. One is detection of defects on a wafer, which is very important. The other is classification of the detected defects, which is done after defect detection as necessary. Recently, it has been necessary to simultaneously detect and classify defects on wafers in order to shorten the wafer inspection time with high resolution. Optical wafer inspection is the most effective method for detecting and classifying a defect and estimating its size in a short time. Optical wafer inspection utilizing scattered light distribution can easily detect and classify a defect since the distribution depends on both the type and size of the defect. The measured scattered light distribution is compared with a database of the previous scattered light distributions using pattern matching in order to classify the defect and estimate its size. Therefore, to achieve optical wafer inspection with scattered light distribution, it is necessary to gather scattered light distribution data for many various samples.The first aim of this study is to develop a defect classification and size estimation method utilizing scattered light distribution. We propose a way for classifying a defect on a wafer and estimating its size. The proposed method uses pattern matching utilizing a parametric eigenspace. The second aim of the paper is to validate the proposed method by applying it to scattered light distribution samples. The light scattering distribution samples are generated by Discrete Dipole Approximation (DDA) simulation. The database of the light scattering distributions is easily created using the simulation.
  • 宮本知幸, 野口聡
    日本シミュレーション学会論文誌(Web) 5 4 59-66 (J-STAGE)  2013年 [査読無し][通常論文]
  • 宮本知幸, 野口聡
    日本シミュレーション学会論文誌(Web) 5 1 1-9 (J-STAGE)  2013年 [査読無し][通常論文]
  • Ryusei Itoh, Yuki Oga, So Noguchi, Hajime Igarashi, Hiroshi Ueda
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 484 484 300 - 304 2013年01月 [査読有り][通常論文]
     
    In recent years, properties of high temperature superconducting (HTS) tapes, especially in-field performance and mechanical strength, have been continuously improved. The HTS tapes have been widely used for high field (>20 T) magnet researches and there are several technical challenges including field attenuation of an HTS magnet by screening currents induced within the HTS tapes. Several publications reported that the screening currents, induced by penetration of self magnetic fields into HTS tapes within an HTS magnet, weakened a field constant of the HTS magnet. The result may demonstrate that the screening current changes an overall current density distribution in HTS tapes and, as a consequence, the generated magnetic field. Therefore, it is necessary to investigate the screening current distribution in an HTS tape. This paper reports numerical simulation of the screening current distribution in an HTS tape of high field magnets using 2D finite element method with the E-J characteristic of the HTS tape taken into account. Self magnetic field distribution and its orientation to the HTS tape are also considered to compute critical currents and locally generated electric fields, two key components to figure out the distribution of screening currents. (C) 2012 Elsevier B.V. All rights reserved.
  • Yuki Oga, So Noguchi, Hajime Igarashi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 22 3 4701604,1-4  2012年06月 [査読有り][通常論文]
     
    Recently, many HTS-SMES systems have been designed and investigated in many countries. They usually consist of some superconducting element coils owing to effectively storing excessively high energy. If one of the superconducting element coils transition into a resistive state, the energy stored in the resistive superconducting element coil has to be immediately dispersed by a shunt resistor to prevent the superconducting conductor from burning. However, the electromagnetic behavior of the HTS-SMES with some resistive superconducting element coils has not yet been well investigated. Therefore, we have developed a simulation code to investigate the electromagnetic behavior of the HTS-SMES magnet after one or more superconducting element coils transitions into the resistive state. In the simulation, the magnetic field analysis and the electrical circuit analysis are coupled with the critical current calculation considering the B - J - theta characteristics of HTS tape. By the electromagnetic simulation, it is indicated that a chain of quenches is caused by the quench of one element coil.
  • Yuki Oga, So Noguchi, Hajime Igarashi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 22 3 4701904 - 4701904 2012年06月 [査読有り][通常論文]
     
    In recent years, many toroidal HTS-SMES consisting of some superconducting element coils have been investigated and designed. In stable operation, the electromagnetic force applying to the superconducting element coils maintains balance because of the toroid structure and the same transport current of each superconducting element coil. However, if one of the superconducting element coils transitioned into a resistive state, the balance of the electromagnetic force would be broken down, and then the huge electromagnetic force would work onto the superconducting element coils. The huge electromagnetic force may overturn the superconducting element coils, and consequently a large accident occurs. However, the behavior of the overturning electromagnetic force after the transition of some superconducting element coils into the resistive state has been not yet well investigated. For the design of the HTS-SMES magnet, it is, therefore, necessary to investigate the overturning electromagnetic force on the design stage. We have developed a simulation code to investigate the behavior of the overturning electromagnetic force on the toroidal HTS-SMES system after the transition of one superconducting element coil into the resistive state. The magnetic field and the circuit analysis are coupled and solved in the developed simulation code.
  • Shinya Matsutomo, Takenori Miyauchi, So Noguchi, Hideo Yamashita
    IEEE TRANSACTIONS ON MAGNETICS 48 2 531 - 534 2012年02月 [査読有り][通常論文]
     
    In electromagnetics education, it is important for beginners, who start to learn electromagnetics, to give an illustration of magnetic field. In this paper we propose a new real-time visualization system. It can visualize a composite image of source materials and their generated magnetic field utilizing the Augmented Reality technique to the users. With this real-time visualization system, electromagnetics learners can observe the visualized magnetic field as a realistic magnetic distribution on real-time and the visualized field changes immediately they move the objects.
  • So Noguchi, SeokBeom Kim
    IEEE TRANSACTIONS ON MAGNETICS 48 2 523 - 526 2012年02月 [査読有り][通常論文]
     
    Magnetic chromatography is an effective system for fine magnetic particle separation because of its strong magnetic field gradients. We have been developing the magnetic chromatography system to separate two or more kinds of fine magnetic particle with different sizes. To evaluate the performances of our developed system, we have also developed a simulation code with taking into account the fluid dynamics and magnetics. It is, however, difficult to consider two or more kinds of fine magnetic particles with different sizes in the simulation, because magnetic interferences between two or more kinds of magnetic particles need to be considered. Therefore, we have newly developed a simulation code to deal with magnetic interferences between two or more kinds of fine magnetic particles.
  • Naoya Terauchi, So Noguchi, Hajime Igarashi, Yoshimi Hatsukade, Saburo Tanaka
    IEEE TRANSACTIONS ON MAGNETICS 48 2 571 - 574 2012年02月 [査読有り][通常論文]
     
    A high temperature superconducting quantum interface device (HTS SQUID) is an extremely sensitive magnetic sensor. The HTS SQUID is required to have a high robustness with respect to magnetic noise for stable operation outside a magnetic shielding room. In order to achieve the high robustness of HTS SQUID, use of a magnetic shield with a superconducting film has been proposed, and its effectiveness has been confirmed in the experiments. In this paper, an electromagnetic field simulation was performed using the 3-D edge finite element method to confirm the effectiveness of the superconducting film magnetic-shield. Since both the SQUID magnetometer and the superconducting film magnetic-shield are made of HTS, it is required to consider the HTS characteristics in the electromagnetic field simulation. Additionally, the SQUID magnetometer has Josephson junction. In this paper, the property of the Josephson junction is also considered. The simulation accuracy depending on the type of the finite element mesh is also investigated.
  • Shinya Matsutomo, So Noguchi, Hideo Yamashita
    IEEE TRANSACTIONS ON MAGNETICS 48 2 527 - 530 2012年02月 [査読有り][通常論文]
     
    To solve electromagnetic field problems by the finite element method, it is necessary for a user to make a mesh in preprocess. However, the made mesh is usually different from that made by the other users, since it depends on the user's experience and knowledge. The mesh strongly affects the accuracy of the analysis result. The adaptive finite element method has been researched in order to address this problem. In this paper, we propose a new mesh generation method utilizing magnetic flux lines in two-dimensional electromagnetic field problem. Utilizing the magnetic flux lines computed with a rough mesh, it is possible to distribute elements with different densities suitable for the electromagnetic field distribution.
  • Atsushi Takada, So Noguchi, Hajime Igarashi
    IEEE TRANSACTIONS ON MAGNETICS 48 2 519 - 522 2012年02月 [査読有り][通常論文]
     
    The ICCG method is widely used to solve a sparse symmetric linear system which results from the finite element method. In order to improve the convergence property of the ICCG method, the introduction of the acceleration factor was proposed. The automatic acceleration factor decision method, using the incomplete Cholesky decomposition of a coefficient matrix, has been previously proposed. However, when employing the previously proposed automatic decision method, much more iterations of ICCG method are sometimes necessary, compared with using the optimum acceleration factor, which minimizes the number of ICCG iterations. In this paper, we propose a new acceleration factor decision method. The proposed method takes into account the condition number of the coefficient matrix. It is well known that the condition number represents the quality of the matrix, so the optimum acceleration factor should be decided to minimize the condition number of the coefficient matrix. However, the condition number of the coefficient matrix is not almost available due to requiring a large memory in computing. Therefore, we develop a new method using submatrix, that does not need a large memory. The procedure and demonstration of the proposed method are described in this paper.
  • Tomoyuki Miyamoto, So Noguchi, Shinya Matsutomo
    ASIASIM 2012, PT I 323 472 - + 2012年 [査読有り][通常論文]
     
    Distinct Element Method (DEM) has been developed for simulating behavior of discontinuous material by considering interaction between distinct elements, i.e. particles. After confirming the validity of DEM through some analysis, we can investigate behavior of material on a chute of a Sorting Machine with DEM. In the previous paper, we have reported that DEM is useful in simulating particles with various shapes, that is sorted by a Sorting Machine. The purpose of this paper is to discuss designing for an effective chute of a Sorting Machine from DEM results. At first, a repose angle of various types of rice in a stock box was simulated and the simulation results were compared with experimental ones. Secondly, the behavior of rice on a chute of a Sorting Machine was simulated and the simulated behavior was compared with actual one. Finally, we designed an effective chute of a Sorting Machine with DEM.
  • Naoya Terauchi, So Noguchi, Hajime Igarashi, Yoshimi Hatsukade, Saburo Tanaka
    SUPERCONDUCTIVITY CENTENNIAL CONFERENCE 2011 36 138 - 143 2012年 [査読有り][通常論文]
     
    An HTS SQUID magnetometer is a highly sensitive magnetic sensor. The SQUID magnetometer is, however, susceptible to magnetic noise. Hence, to enhance the robustness of the SQUID magnetometer with respect to magnetic noise, a cover with a superconducting film magnetic shield has been proposed. The superconducting film magnetic shield improves the robustness with respect to magnetic noise and widens the effective area of the SQUID sensor. It was also confirmed that the shape of the superconducting film magnetic shield affected the effectiveness in the magnetic shield in experiments.In our research, we have carried out a magnetic shielding simulation of the SQUID magnetometer covered with the superconducting film magnetic shield by using a 3D edge finite element method. To clarify the influence of the shape of the superconducting film magnetic shield on the effective area of the SQUID sensor, the simulation concerning a few shapes of the superconducting film magnetic shield was carried out. In order to evaluate the effectiveness of the superconducting film magnetic shield, the supercurrent inside the SQUID magnetometer and the superconducting film magnetic shield are simulated. From the simulation results, it is confirmed that the effective area of the SQUID sensor is widened by attaching the superconducting film magnetic shield over the SQUID ring. (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.
  • Y. Oga, S. Noguchi, H. Igarashi
    ADVANCES IN SUPERCONDUCTIVITY XXIV 27 404 - 407 2012年 [査読有り][通常論文]
     
    When a temperature rise occurs at a local area inside a coil of toroidal HTS-SMES by any reason, a temperature hotspot which results in a thermal runaway appears at the local area. Subsequently, after appearing the local normal zone in the HTS coil, the transport current of the HTS coil decrease since the resistance of HTS coil appears and the current partially flows into a parallel-connecting shunt resistance. However, if the transport current of the normal-transitioned HTS coil is hardly changed, the temperature on the hotspot would rise more and then the normal zone would spread rapidly. It may cause a serious accident due to high stored energy. Therefore, using the numerical simulation, we have investigated the behaviors of the coil current, the critical current, and the temperature in the superconducting element coils of HTS-SMES. Consequently, the temperature of the superconducting element coils rises up extremely when a large heat is generated at a certain area of one of them by any reason. Moreover, there is a possibility that the shunt resister hardly functions for protection since the coil is burned out due to high inductances and low resistance of the superconducting element coil. (C) 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of ISS Program Committee.
  • Naoya Terauchi, So Noguchi, Hajime Igarashi, Yoshimi Hatsukade, Saburo Tanaka
    SUPERCONDUCTIVITY CENTENNIAL CONFERENCE 2011 36 138 - 143 2012年 [査読有り][通常論文]
     
    An HTS SQUID magnetometer is a highly sensitive magnetic sensor. The SQUID magnetometer is, however, susceptible to magnetic noise. Hence, to enhance the robustness of the SQUID magnetometer with respect to magnetic noise, a cover with a superconducting film magnetic shield has been proposed. The superconducting film magnetic shield improves the robustness with respect to magnetic noise and widens the effective area of the SQUID sensor. It was also confirmed that the shape of the superconducting film magnetic shield affected the effectiveness in the magnetic shield in experiments.In our research, we have carried out a magnetic shielding simulation of the SQUID magnetometer covered with the superconducting film magnetic shield by using a 3D edge finite element method. To clarify the influence of the shape of the superconducting film magnetic shield on the effective area of the SQUID sensor, the simulation concerning a few shapes of the superconducting film magnetic shield was carried out. In order to evaluate the effectiveness of the superconducting film magnetic shield, the supercurrent inside the SQUID magnetometer and the superconducting film magnetic shield are simulated. From the simulation results, it is confirmed that the effective area of the SQUID sensor is widened by attaching the superconducting film magnetic shield over the SQUID ring. (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.
  • S. Noguchi, Y. Oga, H. Igarashi
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 471 21-22 1399 - 1403 2011年11月 [査読無し][通常論文]
     
    In recent years, many HTS superconducting magnetic energy storage (HTS-SMES) systems are investigated and designed. They usually consist of some superconducting element coils due to storing excessively high energy. If one of them was quenched, the storage energy of the superconducting element coil quenched has to be immediately dispersed to protect the HTS-SMES system. As the result, the current of the other element coils, which do not reach to quench, increases since the magnetic coupling between the quenched element coil and the others are excessively strong. The increase of the current may cause the quench of the other element coils. If the energy dispersion of the element coil quenched was failed, the other superconducting element coil would be quenched in series. Therefore, it is necessary to investigate the behavior of the HTS-SMES after quenching one or more element coils. To protect a chain of quenches, it is also important to investigate the time constant of the coils. We have developed a simulation code to investigate the behavior of the HTS-SMES. By the quench simulation, it is indicated that a chain of quenches is caused by a quench of one element coil. (C) 2011 Elsevier B.V. All rights reserved.
  • N. Terauchi, S. Noguchi, H. Igarashi
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 471 21-22 1253 - 1257 2011年11月 [査読無し][通常論文]
     
    An HTS SQUID is a high sensitive magnetic sensor. In recent years, the HTS SQUID is widely used in various applications. In some applications, high robustness with respect to magnetic noise is required to realize stable operation at outside of a magnetic shielding room. The target of this paper is a directly coupled HTS dc-SQUID magnetometer. To enhance the robustness of the SQUID magnetometer, use of a superconducting thin film shield has been proposed. The magnetic field directly penetrating the SQUID ring causes the change of the critical current of Josephson junction, and then the SQUID magnetometer transitions into inoperative state. In order to confirm the magnetic shield effect of the superconducting film shield, electromagnetic field simulation with 3D edge finite element method was performed. To simulate the high temperature superconductor, E-J characteristics and c-axis anisotropy are considered. To evaluate the effect of the superconducting film shield, an external magnetic field which is supposed to be a magnetic noise is applied. From the simulation results, the time transition of the magnetic flux penetrating the SQUID ring is investigated and the effect of the superconducting film shield is confirmed. The amplitude of the magnetic flux penetrating the SQUID ring can be reduced to about one-sixth since the superconducting film shield prevents the magnetic noise from directly penetrating the SQUID ring. (C) 2011 Elsevier B.V. All rights reserved.
  • N. Terauchi, S. Noguchi, H. Igarashi
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 471 21-22 1253 - 1257 2011年11月 [査読無し][通常論文]
     
    An HTS SQUID is a high sensitive magnetic sensor. In recent years, the HTS SQUID is widely used in various applications. In some applications, high robustness with respect to magnetic noise is required to realize stable operation at outside of a magnetic shielding room. The target of this paper is a directly coupled HTS dc-SQUID magnetometer. To enhance the robustness of the SQUID magnetometer, use of a superconducting thin film shield has been proposed. The magnetic field directly penetrating the SQUID ring causes the change of the critical current of Josephson junction, and then the SQUID magnetometer transitions into inoperative state. In order to confirm the magnetic shield effect of the superconducting film shield, electromagnetic field simulation with 3D edge finite element method was performed. To simulate the high temperature superconductor, E-J characteristics and c-axis anisotropy are considered. To evaluate the effect of the superconducting film shield, an external magnetic field which is supposed to be a magnetic noise is applied. From the simulation results, the time transition of the magnetic flux penetrating the SQUID ring is investigated and the effect of the superconducting film shield is confirmed. The amplitude of the magnetic flux penetrating the SQUID ring can be reduced to about one-sixth since the superconducting film shield prevents the magnetic noise from directly penetrating the SQUID ring. (C) 2011 Elsevier B.V. All rights reserved.
  • So Noguchi, SeokBeom Kim
    IEEE TRANSACTIONS ON MAGNETICS 47 10 3947 - 3950 2011年10月 [査読有り][通常論文]
     
    A magnetic chromatography is a very useful system for an ion and/or fine magnetic particle separation. Recently, its performance has been enhanced using a superconducting magnet. The superconducting magnet can generate a high magnetic field and its strong magnetic field gradients in a very small flow channel. We have developed the magnetic chromatography system to separate the fine particles. However, its numerical simulation is difficult, since the scale of the fine magnetic particles in fluid is much different from the scale of the superconducting magnet generating the strong magnetic field. In order to accurately simulate the magnetic separation, it is necessary to develop the simulation code dealing with the multiscale. The performance of the developed magnetic chromatography is evaluated by the developed simulation tool, and it is clarified that it is unsuitable for magnetic particle separation. Therefore, a magnetic chromatography is newly designed and its performance is evaluated by the developed simulation tool.
  • So Noguchi, SeokBeom Kim
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21 3 2068 - 2071 2011年06月 [査読有り][通常論文]
     
    Magnetic chromatography is a very useful system for ion and/or fine magnetic particle separation due to strong magnetic field gradients in a very small flow channel. We have developed the magnetic chromatography system to separate the ions and fine particles. It is, however, difficult to separate the ions or the magnetic particles using the developed magnetic chromatography. It makes the strong magnetic field gradients in the flow channel, but the alternate direction of the gradient is not suitable for magnetic separation. Therefore, we have newly designed a novel magnetic column with ferromagnetic nano-wires. In this paper, the new magnetic column is presented, and the magnetic field and its gradients in the flow channel are investigated.
  • Keisuke Yoshizawa, So Noguchi, Hajime Igarashi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21 3 2088 - 2091 2011年06月 [査読有り][通常論文]
     
    In this paper, an influence of a magnetic property of a ferromagnetic shield on design of a high field magnet, which generates high magnetic field with high homogeneity, such as NMR and MRI, is described. The NMR and MRI magnets often need the magnetic shield to protect an environment and to reduce a stray magnetic field. An iron shield used as a general magnetic shield typically has a nonlinear magnetic property. In magnetic analysis for the magnet design, we have to take into account the nonlinearity of the magnetic property of iron to compute the accurate magnetic field, since the ferromagnetic shield is exposed to so high magnetic field. That is, the iron is saturated in high magnetic field. So far the design of the high field magnets with the ferromagnetic shield exposed to over 2 T has been less reported. Recently, it was reported that the nonlinear magnetic properties of iron were measured at high magnetic fields over 2 T. The difference among the magnetic fields of the high field magnets with the ferromagnetic shield, computed by the finite element method with a few magnetization curves, is investigated.
  • So Noguchi, Makoto Tsuda
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21 3 2279 - 2282 2011年06月 [査読有り][通常論文]
     
    Large-inductance DC reactors are often required in practical factories, and superconducting magnets represent an interesting alternative for the construction of such devices. It is therefore useful to obtain optimized designs for DC reactors, particularly for the minimization of the winding volume under many constraints. The superconducting magnets of DC reactors can be operated at higher temperature than that of SMES, since the rated current in the case of DC reactors is much smaller. To operate at high temperature (77 K) makes the coolant cost low. However, the flux flow loss becomes large at 77 K, and then it has to be taken into account at the design stage. In this paper, the optimized configurations of toroidal superconducting magnets for DC reactor are presented and the configurations of HTS conductor are investigated under taking the flux flow loss into account.
  • Noguchi So, Kim SeokBeom
    IEEE Transactions on Magnetics 47 5 898 - 901 IEEE : Institute of Electrical and Electronics Engineers 2011年05月 [査読有り][通常論文]
     
    Magnetic separation is a very useful tool in medicine manufacturing and sludge disposal, and we have developed the magnetic chromatography system, which separates the magnetic particles or the ions from fluid due to its strong magnetic field gradients in the very small flow channel. There are many fine ferromagnetic wires on the wall of the developed magnetic column. A superconducting magnet applies a strong magnetic field to the magnetic column, and fine ferromagnetic wires make strong magnetic field gradients. It was, however, impossible to accurately evaluate the performance of the developed magnetic column due to the absence of a good simulation method. In order to enhance the accuracy of the simulation, it is necessary to couple the fluid dynamics simulation with the magnetic field simulation. Therefore, we have developed a simulation code dealing with the fluid dynamics, solving Navier-Stokes, control volume, and magnetic field equations simultaneously, and compared the simulation result to the experimental one to verify the validity.
  • Noguchi So, Inaba Tomoaki, Igarashi Hajime
    IEEE Transactions on Magnetics 47 5 1330 - 1333 IEEE : Institute of Electrical and Electronics Engineers 2011年05月 [査読有り][通常論文]
     
    When visualizing a 3-D electromagnetic field analysis result, physical quantity on a surface or a cross section of objects is visualized mostly. It is, however, desired to observe the physical quantity and the phenomenon inside the objects in 3-D space. In this paper, the method to visualize the physical quantity inside the objects with a volumetric display is proposed. The volumetric display is based on a stack of liquid crystal displays (LCDs), and developed to separately display the images on the LCDs. With the volumetric display, the physical quantity, which changes on different cross sections of the objects in 3-D, can be visualized simultaneously. The volumetric display is also used for image comparison. In order to compare the results of magnetic field analysis, usually each image is compared by overlappingly visualizing these. However, it is easy to visualize the images and compare these, using the volumetric display. The volumetric display is a useful tool for postprocessing of the electromagnetic field analysis.
  • So Noguchi, Seok Beom Kim
    APPLIED ELECTROMAGNETIC ENGINEERING FOR MAGNETIC, SUPERCONDUCTING AND NANOMATERIALS 670 3 - + 2011年 [査読有り][通常論文]
     
    We have investigated the stability of 2.0 GJ toroidal HTS-SMES, which consists of 90 element coils wound from YBCO tape. If one or more element coils are quenched, the storage energy reduces due to change of the magnetic field distribution. A series of quench for some element coils may occur, when the energy of the quenched coil cannot be consumed adequately. The simultaneous quench of some element coil may cause the system down. Therefore, it is necessary to investigate the simultaneous quench properties.
  • Y. Motooka, S. Noguchi, H. Igarashi
    APPLIED ELECTROMAGNETIC ENGINEERING FOR MAGNETIC, SUPERCONDUCTING AND NANOMATERIALS 670 318 - 324 2011年 [査読無し][通常論文]
     
    We have previously proposed an automatic hexahedral mesh generator. It is necessary to understand about the quality and characteristic of the generated mesh to perform hexahedral edge finite element analysis in electromagnetic. Therefore, we have compared high-quality meshes with poor-quality meshes, and investigated about the factors that affect the accuracy and the computation time. In addition, we investigated about the effect of the templates used in the proposed method. We will conclusively apply the result to improving the automatic hexahedral mesh generator.
  • S. B. Kim, R. Iwamoto, K. Kataoka, S. Noguchi, H. Okada
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 20 1804 - 1807 2010年11月 [査読無し][通常論文]
     
    The magnetic chromatography is a very useful system for an ion and/or fine magnetic particle separation because it has strong magnetic field gradients even in a very narrow flow channel. We have not only developed the magnetic chromatography system to separate the fine particles and ions, but also the numerical analysis code based on the fluid dynamics and electromagnetism to investigate the separating characteristics and to optimize design of magnetic column. In this study, the simple experiments using a superconducting magnet with a large room-temperature-bore and a micro-scale magnetic column consisting of ferromagnetic wires were carried out to understand the ions separation. The cobalt chloride (CoCl(2)) and the nickel sulfate (NiSO(4)) were used as ions, and the magnetic field and length of magnetic column were used as a parameter in an experiment and an analysis. It can be expected that the ion mobility of a single and complex are quite different, and the ability of the separation will be improved by increasing the column length without external magnetic field. (C) 2010 Elsevier B.V. All rights reserved.
  • S. B. Kim, R. Iwamoto, K. Kataoka, S. Noguchi, H. Okada
    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 20 1804 - 1807 2010年11月 [査読無し][通常論文]
     
    The magnetic chromatography is a very useful system for an ion and/or fine magnetic particle separation because it has strong magnetic field gradients even in a very narrow flow channel. We have not only developed the magnetic chromatography system to separate the fine particles and ions, but also the numerical analysis code based on the fluid dynamics and electromagnetism to investigate the separating characteristics and to optimize design of magnetic column. In this study, the simple experiments using a superconducting magnet with a large room-temperature-bore and a micro-scale magnetic column consisting of ferromagnetic wires were carried out to understand the ions separation. The cobalt chloride (CoCl(2)) and the nickel sulfate (NiSO(4)) were used as ions, and the magnetic field and length of magnetic column were used as a parameter in an experiment and an analysis. It can be expected that the ion mobility of a single and complex are quite different, and the ability of the separation will be improved by increasing the column length without external magnetic field. (C) 2010 Elsevier B.V. All rights reserved.
  • So Noguchi, Makoto Tsuda
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 20 3 1814 - 1817 2010年06月 [査読有り][通常論文]
     
    Large-inductance DC reactors are often required in practical factories, and superconducting magnets represent an interesting alternative for the construction of such devices. It is therefore useful to obtain optimized designs for DC reactors, particularly for the minimization of the winding volume under many constraints. In this paper the optimized configurations of toroidal superconducting magnets for DC reactor are presented and the configurations for SMES are compared.
  • So Noguchi, SeokBeom Kim, Katuhito Kataoka
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 20 3 961 - 964 2010年06月 [査読有り][通常論文]
     
    The magnetic chromatography is a very useful system for an ion and/or fine magnetic particle separation due to its strong magnetic field gradients in a very small flow channel. We have developed the magnetic chromatography system to separate the fine particles and ions. However, its numerical simulation is difficult, since the scale of the ions or fine particles in fluid is much different from the scale of the superconducting magnet generating the strong magnetic field. In order to accurately simulate the magnetic separation, it is necessary to develop the simulation code dealing with the multi-scale problem.
  • SeokBeom Kim, Yuichi Okimoto, Satoru Murase, So Noguchi, Hidehiko Okada
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 19 3 2152 - 2156 2009年06月 [査読有り][通常論文]
     
    The magnetic chromatography (MC) is a very useful system for an ion and/or fine magnetic particle separation due to its strong magnetic field gradients in a very small flow channel. We have not only developed the MC system to separate the fine particles and ions, we have also developed the numerical analysis computer code based on the fluid dynamics and electromagnetism to investigate the separating characteristics and to optimize design of magnetic column. In this paper, we studied MC technology for magnetic particles and ion separations using micro-scale magnetic column with ferromagnetic wires experimentally. The influences of the strength of magnetic gradient, flow velocity and coefficient of viscosity of solvent were studied by the developed computer code.
  • Hiroaki Date, So Noguchi, Masahiko Onosato, Satoshi Kanai
    IEEE TRANSACTIONS ON MAGNETICS 45 3 1352 - 1355 2009年03月 [査読有り][通常論文]
     
    This paper describes a method for flexibly controlling the properties of a given multimaterial tetrahedral mesh for finite-element analysis. Our method is based on multiresolution techniques. A given mesh is first subdivided and then simplified so that the resulting mesh satisfies the user-specified thresholds for mesh properties (element size, shape, valence, and geometric tolerance). Once the simplification is completed, mesh resolution and density can be modified quickly by using level of detail.
  • So Noguchi, Youichi Inaba, Hajime Igarashi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 18 2 762 - 765 2008年06月 [査読有り][通常論文]
     
    This paper describes an optimal design method for SMES coils wound with high temperature superconducting tapes. Commonly, on the design stage of a SMES coil, its configuration is optimized to reduce the winding' volume and the weight under taking into account the electromagnetic characteristics of high temperature superconducting tapes. The better configuration can be optimally designed to taken into account its thermal characteristics. So, we propose an optimal design method for SMES coils wound with Bi2223/Ag tape taking into account both electromagnetic and thermal characteristics. In this paper, the designs of 72 MJ toroidal SMES coil are investigated using the Simulated Annealing as an optimization method and the Finite Element Method as a thermal analysis method.
  • Tomoyuki Miyamoto, So Noguchi, Hideo Yamashita
    IEEE TRANSACTIONS ON MAGNETICS 44 6 1026 - 1029 2008年06月 [査読有り][通常論文]
     
    In general, many optimal solutions exist to a multipurpose optimal design problem, and the selection of one appropriate solution from the optimal set is a challenging task. In this work, a method applying Game Theory for decision-making from the Pareto-optimal solutions is proposed. From a practical point of view, more than two objectives frequently have to be taken into account. The optimal design method presented in this paper is able to deal with such problems. The proposed method was applied to an optimal design problem with multiple objectives to confirm its usefulness.
  • 平畠 将士, 野口 聡, 五十嵐 一, 山下 英生
    電気学会論文誌. B, 電力・エネルギー部門誌 = The transactions of the Institute of Electrical Engineers of Japan. B, A publication of Power and Energy Society 127 11 1205 - 1212 一般社団法人 電気学会 2007年11月01日 [査読無し][通常論文]
     
    This paper presents analytical calculation of magnetic flux line from hexahedral edge finite element analysis and its allocation using the Bubble System for visualization. Most of methods to draw magnetic flux lines can't take their distribution into sufficient consideration. As a result, such visualizations bring out observer's misunderstanding about the magnetic field and the phenomenon. Therefore, the method to appropriately allocate the magnetic flux lines in a space using the Bubble System is proposed. In the proposed method, the bubble's radius of the Bubble System depends on the magnetic flux density to consider the density of lines. The proposed method using the Bubble System can visualize magnetic flux lines appropriately. Then, the observer can correctly grasp the magnetic field and the phenomenon.
  • 宮本 知幸, 野口 聡, 山下 英生
    シミュレーション = JOURNAL OF THE JAPAN SOCIETY FOR SIMULATION TECHNOLOGY 26 2 121 - 126 日鉄技術情報センタ- 2007年06月15日 [査読無し][通常論文]
     
    In this paper, we propose a method applying Game Theory for decision-making from the Pareto-optimal solutions. In general, many optimal solutions exist to a multi-purpose optimal design problem, and to select one appropriate solution from the optimal set is a challenging task. therefore, two kinds of the non-zero-sum games without cooperation and with bargaining are applied to the multi-purposed design problem. As the results, the approach using the Game Theory is effective in the information-providing for selecting a suitable solution for multi-purposed optimal design problem. Additionally, the multiple-designers' intention, at the design stage, can be clearly and effectively reflected by the proposed approach.
  • So Noguchi, Nobuki Kawawada, Hajime Igarashi, Atsushi Ishiyama, Nagato Yanagi, Shinsaku Imagawa
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17 2 2490 - 2493 2007年06月 [査読有り][通常論文]
     
    Aluminum stabilized superconductors are used in accelerators, SMES, and fusion devices, such as the LHD helical coils. These superconductors have large cross-sectional area of high purity aluminum to improve their stability. However, one of the important properties of these superconductors is the transient stability, which is caused by a long duration of transport current transfer from the superconducting strands into the aluminum in a normal state region. Once a normal zone is initiated in such superconductors, excess joule heat is generated in a small region of the aluminum stabilizer near the superconducting strands during the transport current diffusion time. It hence deteriorates the transient stability. Therefore, it is important to investigate the characteristics of the transient stability by numerical analysis. The latest experiments of the LHD helical coil conductor showed an asymmetrical propagation of normal zone along the longitudinal direction of the conductor. The Hall effect is clearly one of the causes of this phenomenon. The Hall effect prevents the transport current from transferring between the superconducting strands and the aluminum stabilizer. It causes the asymmetrical transport current distribution, and affects the stability of the superconductor. In order to simulate the normal zone propagation in the superconductor more precisely and to clarify the cause of the asymmetrical propagation, we have developed a 2D finite element analysis code taking account of the Hall effect and investigated the characteristics of the normal zone propagation of large aluminum stabilized superconductors.
  • So Noguchi, Takanori Tanikawa, Hajime Igarashi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17 2 1835 - 1838 2007年06月 [査読有り][通常論文]
     
    The resistive Superconducting Fault Current Limiters are very attractive devices for electric power circuits. We have investigated the operating properties of a parallelized superconducting fault current limiter made from YBCO thin film and gold film on sapphire substrate by numerical simulation. In order to improve the operating properties and the stability, the YBCO films need to be parallelized. However, it is necessary to investigate whether a few sheets of YBCO film with different critical current density will deteriorate the device's operating properties and stability. That is, when the fault current occurs in power circuit, all YBCO films with different critical current density have not simultaneously quenched. It causes the deterioration of the operating properties. Therefore, it is necessary to investigate the influence of the imbalanced critical current density on the quench characteristics of the parallelized superconducting fault current limiter by numerical simulation. The simulation is performed by a newly developed code coupling the thermal diffusion and the current circuit. It takes into account the E-J power low depending temperature, obtained by experiments. The current limiting properties and the recovery properties are evaluated from quench behavior when the YBCO films have some inhomogeneities. Moreover, the influence of the thickness of gold film on the current limiting properties is also investigated. To grasp such properties is required when the resistive fault current limiter using YBCO thin film is designed.
  • Hirotomo Fujimori, So Noguchi, Hajime Igarashi, Hideo Yamashita
    IEEE TRANSACTIONS ON MAGNETICS 43 4 1505 - 1508 2007年04月 [査読有り][通常論文]
     
    In this paper, an automatic hexahedral mesh generation method is presented in order to control the element size along each direction. By utilizing Ellipsoidal Bubbles as mesh density data, the present method can generate the mesh with flat elements for analysis, including very thin domain such as eddy current regions of conductor, motor air gaps, and so on. In order to verify the effectiveness of the present method, the finite element analysis was actually performed.
  • 藤森 寛朝, 野口 聡, 五十嵐 一
    電気学会論文誌. D, 産業応用部門誌 = The transactions of the Institute of Electrical Engineers of Japan. D, A publication of Industry Applications Society 127 3 293 - 299 一般社団法人 電気学会 2007年03月01日 [査読無し][通常論文]
     
    This paper presents an adaptive mesh generation with parameterized learning. The present method does not need to perform iterative processes of field analysis in contrast with the conventional adaptive meshing methods. The present method evaluates mesh qualities for each element by means of evaluation function, which is weighted linear combination of shape and area of elements, distance from material corners and so on. The element which has the worst value of the evaluation function is divided into a few elements according to its shape, and this procedure is repeated until the prescribed number of elements is obtained. By using the simple Genetic Algorithm (sGA), the weighting coefficients are optimized through learning with example models such that the resultant mesh has the lowest numerical error.
    The good mesh can be obtained without time-consuming computation, since the weight values for the mesh features are learned by the sGA. The present method would allow us to realize effective design and development of electromagnetic machine and devices.
  • Tomohiro Yanagawa, Kazufumi Kaneda, So Noguchi, Hideo Yamashita
    JOURNAL OF MATERIALS PROCESSING TECHNOLOGY 181 1-3 31 - 35 2007年01月 [査読有り][通常論文]
     
    It is necessary to accurately comprehend the characteristics of high-temperature superconducting bulk in application. However, the accurate simulation of supercurrent in high-temperature superconducting bulk is difficult even by adopting the finite element method. The equivalent electrical conductivity of high-temperature superconducting bulk is introduced for the supercurrent analysis. Due to the strong non-linearity of the conductivity, the analytical convergence of the non-linear equation solvers, e.g., the Newton-Raphson method deteriorates. Consequently, the unreasonable supercurrent is observed in the results. Therefore, in this paper, the accuracy of the supercurrent analysis in the high-temperature superconducting bulk is discussed and a new method is proposed for the accurate high-temperature superconducting bulk simulation, and then the validity of the proposed method is discussed by analyzing two example models, a disk and a sphere. (c) 2006 Elsevier B.V. All rights reserved.
  • Felipe Campelo, So Noguchi, Hajime Igarashi
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 16 2 1316 - 1319 2006年06月 [査読有り][通常論文]
     
    When designing high-field superconducting magnets, such as the ones used in nuclear magnetic resonance, one is often interested in using the minimum winding volume, in order to reduce the construction costs. On the other hand, a highly homogeneous, highly regulated magnetic field is an essential requirement for this kind of system. Moreover, small variations in the design parameters are unavoidable in the construction of any equipment, and must be taken into account during the design process. Due to these many requirements, the design of magnets with high field homogencity is a very difficult task for traditional optimization methods.Optimization methods based in the artificial immune systems paradigm are usually able to perform global as well as local exploration of the search space. The local search feature can be used to perform an estimation of the sensitivity of the candidate solutions, thus enabling the algorithm to search for points that represent robust devices at a reasonable computational cost.In this work, we explore the design of a high-field, highly homogeneous superconducting magnets by using an immune-based robust optimization algorithm. The algorithm is described, and applied to the optimization of the device. The analysis of the results shows the validity of the proposed method.
  • Nobuki Kawawada, So Noguchi, Hajime Igarashi, Atsushi Ishiyama, Nagato Yanagi, Shinsaku Imagawa
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 16 2 1717 - 1720 2006年06月 [査読有り][通常論文]
     
    Aluminum stabilized superconductors are used in accelerators, SMES, and fusion devices, such as the LHD helical coils. These superconductors have large-cross sectional area of high purity aluminum to improve their stability. However, one of the important properties of these superconductors is the transient stability, which is caused by a long duration of transport current transfer from the superconducting strands into the aluminum in a normal-state region. Once a normal zone is initiated in such superconductors, excess joule heat is generated in a small region of the aluminum stabilizer near the superconducting strands during the transport current diffusion time. It hence deteriorates the transient stability. Therefore, it is important to investigate the characteristics of the transient stability by numerical analysis. The latest experiments of the LHD helical coil conductor show an asymmetrical propagation of normal zone along the longitudinal direction of the conductor.The Hall current generation is clearly one of the causes of this phenomenon. The Hall current generation prevents the transport current from transferring between the superconducting strands and the aluminum stabilizer. It causes the asymmetrical transport current distribution, and affects the stability of the superconductor. In order to simulate the normal-zone propagation in the superconductor more preciously and to clarify the cause of the asymmetrical propagation, we have developed a 2D finite element analysis code taking account of the Hall effect and investigated the transient stability of large aluminum stabilized superconductors.
  • Yanagawa Tomohiro, Kaneda Kazufumi, Ishiyama Atsushi, Noguchi So, Yamashita Hideo
    IEEE transactions on magnetics 42 4 751 - 754 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS 2006年04月 [査読無し][通常論文]
     
    It is difficult to accurately simulate supercurrent in high-temperature superconducting bulk even by adopting the finite-element method. The equivalent electrical conductivity of high-temperature superconducting bulk, which has a strong nonlinearity according to the E-J power law, is introduced for the supercurrent analysis. However, the strong nonlinearity results in bad convergency of the nonlinear equation solvers, i.e., the Newton-Raphson (NR) method. Consequently, the unsuitable and/or undulating supercurrent is observed. Therefore, in this paper, the accuracy of the supercurrent analysis in the high-temperature superconducting bulk is discussed and a new method is proposed for the accurate high-temperature superconducting bulk simulation. Then, the method combined a line search with the NR method is adopted as a nonlinear equation solver, and the improvement of convergency and computation time are investigated.
  • Matsutomo Shinya, Miyamoto Tomoyuki, Kaneda Kazufumi, Noguchi So, Yamashita Hideo
    IEEE transaction on magnetics 42 4 567 - 570 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS 2006年04月 [査読無し][通常論文]
     
    The finite-element analysis is widely used in design stage of electromagnetic apparatuses. The analysis accuracy depends on the characteristics of the finite-element mesh, e.g., number of nodes, number of elements and shape of elements. Recently, the adaptive finite-element analysis is one of the most promising numerical analysis techniques. In process of the adaptive finite-element method, the error evaluation is one of the important schemes. In this paper, a new error evaluation scheme, which is suitable for electromagnetic problems, is proposed The proposed error evaluation method is then applied to two-dimensional and three-dimensional magnetostatic field problems for its verification.
  • Campelo Felipe, Guimarães Frederico G., Igarashi Hajime, Ramírez Jaime A., Noguchi So
    IEEE transactions on magnetics 42 4 1111 - 1114 IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS 2006年04月 [査読無し][通常論文]
     
    Some optimization algorithms based on theories from immunology have the feature of finding an arbitrary number of optima, including the global solution. However, this advantage comes at the cost of a large number of objective function evaluations, in most cases, prohibitive in electromagnetic design. This paper proposes a modified version of the artificial immune network algorithm (opt-AINet) for electromagnetic design optimization. The objective of this modified AINet (m-AINet) is to reduce the computational effort required by the algorithm, while keeping or improving the convergence characteristics. Another improvement proposed is to make it more suitable for constrained problems through the utilization of a specific constraint-handling technique. The results obtained over an analytical problem and the design of an electromagnetic device show the applicability of the proposed algorithm.
  • S Noguchi, A Ishiyama, S Akita, H Kasahara, Y Tatsuta, S Kouso
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 15 2 1927 - 1930 2005年06月 [査読無し][通常論文]
     
    Recently, the properties of high temperature superconducting tapes have been in advance and high temperature superconducting magnets have been constructed and demonstrated. However, the high temperature superconducting tapes have different thermal characteristics compared with low temperature superconducting wires. Therefore, it is necessary to consider these characteristics of high temperature superconducting tapes at the magnet design stage. We proposed an optimal design method for superconducting coils wound with Bi2223/Ag tapes. In this paper, the configuration of 72 MJ SMES coils wound with Bi2223/Ag tapes are optimized.
  • S Noguchi, T Maeda, K Yamashita, H Yamashita, Cingoski, V
    IEEE TRANSACTIONS ON MAGNETICS 41 5 1664 - 1667 2005年05月 [査読無し][通常論文]
     
    An automatic mesh generator for hexahedral elements has already been proposed. However, the application of this generator to a model with both the hexahedral and the cylindrical objects results with generated meshes with large number of flat finite elements. It is known that a large number of flat elements lead to much lengthy finite element analysis (FEA) and lower accuracy of the obtained results. Therefore, the development of the versatile and high-quality automatic hexahedral mesh generator for models consisting hexahedral and cylindrical objects in the same model is strongly desired. In the proposed generation method, where the geometrical change of the model is employed, the generated mesh is composed mainly of well-shaped hexahedral elements. Moreover, the same number of boundary nodes for imposing periodical boundary conditions can be generated.
  • S Noguchi, T Yoshigai, H Yamashita
    IEEE TRANSACTIONS ON MAGNETICS 41 5 1820 - 1823 2005年05月 [査読無し][通常論文]
     
    This paper describes an analytical method for the computation of magnetic flux lines in three-dimensional (3-D) space from hexahedral edge finite element results and its visualization. Using the results obtained from the edge finite element analysis by hexahedral mesh and the magnetic flux line equation in 3-D space, the sequence of line segments that construct the magnetic flux line is computed as faithfully as possible. The features of the proposed method are short computation time and high accuracy, providing cheap and efficient computation. The procedure and three examples to present the usefulness of the proposed method are described.
  • T Tsuchiya, S Noguchi, H Yamashita
    JOURNAL OF MATERIALS PROCESSING TECHNOLOGY 161 1-2 10 - 15 2005年04月 [査読無し][通常論文]
     
    Very large current composite superconductors are used in SMES coils and fusion applications. These superconductors have large cross-sectional areas of high purity aluminum to improve their stability and to enhance the overall current density. Once a normal zone is initiated in such superconductors, the current transfers from the superconducting strands to the aluminum stabilizer according to the temperature distribution. The time constant of current diffusion in the aluminum stabilizer, however, is very long due to the low electrical resistivity of aluminum. Therefore, excess joule heat is generated in a small region of aluminum stabilizer near superconducting strands and the temperature increases locally. Therefore, some 2D numerical analyses have been carried out in order to investigate the transient stability. However, recently, the performance of computer is enhanced and a huge numerical simulation becomes possible to be carried out. Therefore, we have developed a 3D finite element analysis codes and carried out some analyses. Finally, we compared the results of 2D and 3D analyses. (c) 2004 Published by Elsevier B.V.
  • T Maeda, S Noguchi, H Yamashita, Cingoski, V
    JOURNAL OF MATERIALS PROCESSING TECHNOLOGY 161 1-2 101 - 106 2005年04月 [査読無し][通常論文]
     
    We have proposed an automatic mesh generator for hexahedral elements previously. This technique can be applied to almost all models. However, if it is applied to a cylindrical model, its mesh, which contains many flat elements, is generated. Using such mesh, it is time consuming to perform finite element analysis (FEA) and its result may not have enough accurate. Therefore, an automatic mesh generator for cylindrical models is required. In this paper, the hexahedral mesh generation method for cylindrical models is proposed. In this method, by using cylindrical coordinate system, the mesh with well-shaped hexahedral elements is generated even for complicated analysis domain. (c) 2004 Elsevier B.V. All rights reserved.
  • MEG Source Localization by using Artificial Neural Network
    JSAEM Studies in Applied Electromagnetics and Mechanics 15 133 - 136 2005年 [査読無し][通常論文]
  • A New Method of Error Estimation for Adaptive Finite Element Method
    JSAEM Studies in Applied Electromagnetics and Mechanics 15 137 - 142 2005年 [査読無し][通常論文]
  • 野口 聡, 松林 豊, 山下 英生
    シミュレーション = JOURNAL OF THE JAPAN SOCIETY FOR SIMULATION TECHNOLOGY 23 3 212 - 220 日鉄技術情報センタ- 2004年09月15日 [査読無し][通常論文]
     
    In this paper, we propose a new interactive visualization system with force feedback device in 3D electromagnetics. The proposed system can not only visualize some kinds of field distribution, but also make electro-magnetic force perceptible to a user simultaneously, immediately he changes the position of movable object. Perceiving electromagnetic force and observing field distribution help users, who are electromagnetic learners and electric apparatus designers, understand of electromagnetic phenomenon more deeply than a common visualization system with only graphical visualization from computation results. And, the proposed system can interactively visualize the magnetic vector potential distribution, the magnetic flux density distribution, the magnetic flux lines and the magnetic flux density vector or any combination of them.
  • T Tsuchiya, S Noguchi, H Yamashita, A Ishiyama, N Yanagi, T Mito
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 14 2 1330 - 1333 2004年06月 [査読無し][通常論文]
     
    Very-large-current composite superconductors are used in SMES coils and fusion applications. These superconductors have large cross-sectional areas of high purity aluminum to improve their stability. Once a normal zone is initiated in such superconductors, the current transfers from the superconducting strands to the aluminum stabilizer according to the Maxwell's equations and the temperature distribution. However, the time constant of current diffusion in the aluminum stabilizer is very long as electrical resistivity of aluminum is very low. Therefore, excess Joule heating is generated in a small region of aluminum stabilizer near superconducting strands, and the temperature increases locally. Some 2D numerical analyses have been carried out in order to investigate the transient stability of the superconductor applied to the Helical Coil of LHD in National Institute for Fusion Science. But, as the performance of computers have improved, huge numerical simulations are new feasible. So we wrote a 3D finite element analysis code ourselves to carry out some now analyses that we compared with 2D analysis.
  • S Noguchi, Y Matsubayashi, H Yamashita, Cingoski, V
    IEEE TRANSACTIONS ON MAGNETICS 40 2 1382 - 1385 2004年03月 [査読有り][通常論文]
     
    This paper describes an interactive visualization system with force feedback device in three-dimensional (3-D) electromagnetics. We present an extension and improvement of the previously developed two-dimensional (2-D) interactive visualization system used for visualization of various 2-D field distribution maps with arbitrarily movable objects inside the analyzed region. We improve our 2-D visualization system to deal with real 3-D models. Moreover, we knew that perceiving electromagnetic force along with observing various 3-D field distribution maps could significantly help users to better understand the complex electromagnetic phenomenon. Driven by these ideas, we have developed a 3-D interactive visualization system with force feedback device for fast and easy perception of the electromagnetic force and electromagnetic field distribution maps for 3-D models with movable objects.
  • S Matsutomo, S Noguchi, H Yamashita, S Tanimoto
    IEEE TRANSACTIONS ON MAGNETICS 40 2 1232 - 1235 2004年03月 [査読有り][通常論文]
     
    Optimal design techniques, which consist of numerical analysis and optimization technique, are commonly used for enhancing the efficiency and,for reducing the noise of electromagnetic device. In the optimal design techniques, it is required that the exact solution of the analysis and the precise characteristic of the electromagnetic devices should be obtained. However, usually it is impossible to make the exact model of an electromagnetic device and to remove the numerical error of the numerical analysis. This is one of the reasons why the optimal design techniques has not been more widely utilized. In this paper, a new concept for optimal design considering the accuracy of the analysis is proposed. The proposed optimal design method considers the accuracy of the analysis and indicates multiple solutions. To verify its usefulness, in this paper, an example using the proposed method is shown.
  • T Maeda, S Noguchi, H Yamashita, Cingoski, V
    IEEE TRANSACTIONS ON MAGNETICS 40 2 973 - 976 2004年03月 [査読有り][通常論文]
     
    In this paper, an automatic hexahedral mesh generator for rotating machines is proposed. In the proposed method, hexahedral mesh with well-shaped elements is generated by means of transformation of coordinates of the analysis model. The main feature of this method is its applicability for meshing models with cylindrical shape due to provided coordinate transformation forward and backward between Cartesian coordinate system and the cylindrical coordinate system. The previously proposed hexahedral mesh generation method could easily control the mesh density and generate well-shaped elements. However, applying that method to rotating machines, due to their cylindrical shape always generates bad-shaped elements. Therefore, we improved and extended this mesh generation method to become fully applicable for meshing complex cylindrically shaped domains of the rotating machines. By using the newly proposed method, a well-shaped hexahedral finite element meshes could be generated suitable for fast and accurate finite element analysis of any cylindrically shaped domains.
  • S Noguchi, Y Matsubayashi, H Yamashita, Cingoski, V
    INTERNATIONAL JOURNAL OF APPLIED ELECTROMAGNETICS AND MECHANICS 19 1-4 385 - 390 2004年 [査読無し][通常論文]
     
    This paper describes an interactive visualization system with force feedback device in 3D electromagnetics. Previously, we developed the interactive system that can not only visualize some kinds of field distribution, but make a user feel the magnetic force in 2D electromagnetics simultaneously. The aim of the previous system is mainly educational because physical behavior in 2D electromagnetics is simpler than that of 3D. However, the 3D interactive visualization system with force feedback is required for design, education and so on, since the realistic model is necessarily used. Therefore, we have developed the 3D interactive visualization system with force feedback device.
  • An Optimal Design Method for Configuration of HTS SMES Coils
    Institute of Physics, Conference Series Number 181 [CD-ROM] 1124 - 1131 2004年 [査読無し][通常論文]
  • An optimization method for design of PM motor by using Voltage Driven Finite Element Method and Genetic Algorithm
    International Journal of Applied Electromagnetics and Mechanics 19 1-4 433 - 436 2004年 [査読無し][通常論文]
  • Investigation of Error Estimation and Mesh Refinement for Adaptive Finite Element Method
    Computational Engineering I -Advances in Continuum Mechanics and Electromagnetics- 291 - 298 2004年 [査読有り][通常論文]
  • Investigation on Convergency of Non-nested Multigrid Method for High Frequency Electromagnetic Problems
    Computational Engineering I -Advances in Continuum Mechanics and Electromagnetics- 133 - 139 2004年 [査読有り][通常論文]
  • Spasov Vasil, Noguchi So, Yamashita Hideo
    電気学会論文誌. D, 産業応用部門誌 = The transactions of the Institute of Electrical Engineers of Japan. D, A publication of Industry Applications Society 123 10 1169 - 1175 一般社団法人 電気学会 2003年10月01日 [査読無し][通常論文]
     
    This paper presents a fast electromagnetic field analysis by the 3D geometric multigrid method with edge elements. The multigrid method uses a symmetric Gauss-Seidel smoother with Conjugate Gradient acceleration. The convergence and computation speed of the V-cycle, W-cycle and full multigrid method using this smoother are compared with the conventional multigrid using Gauss-Seidel. Comparison is also made between the multigrid method and the ICCG method which is commonly used in the finite element analysis. The efficiency of the multigrid method is analyzed for meshes whose maximum aspect ratios vary in a wide range. It is proven that the multigrid method with the accelerated symmetric Gauss-Seidel outperforms the multigrid with Gauss-Seidel and the ICCG method. The multigrid method with the accelerated symmetric Gauss-Seidel shows stable convergence rate that does not deteriorate for bad quality meshes. It is robust against mesh distortion and parameter variations and is much faster than the conventional multigrid with Gauss-Seidel and the finite element method using ICCG.
  • S Noguchi, H Yamashita, A Ishiyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 13 2 1856 - 1859 2003年06月 [査読有り][通常論文]
     
    Recently, the properties of high temperature superconducting (HTS) tapes have been in advance and HTS magnets have been constructed and demonstrated. However, the HTS tapes have thermal different characteristics compared with the low temperature superconducting (LTS) wires. Moreover, Bi2223/Ag tapes and YBCO coated conductors have the different properties about the dependence on the degree of external magnetic field. Therefore it is necessary to consider these characteristics of HTS tapes at magnet design stage. We proposed an optimal design method for superconducting coils using Bi2223/Ag tapes. And the proposed configuration is optimized by using the simulated annealing (SA), which is one of the optimization algorithms, under a lot of constraints such as B-I characteristic, storage energy, and so on. The details of the optimization method and an example of its application to SMES coils (72 NU) using YBCO coated conductors are shown.
  • S Noguchi, H Yamashita, A Ishiyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 13 2 1856 - 1859 2003年06月 [査読無し][通常論文]
     
    Recently, the properties of high temperature superconducting (HTS) tapes have been in advance and HTS magnets have been constructed and demonstrated. However, the HTS tapes have thermal different characteristics compared with the low temperature superconducting (LTS) wires. Moreover, Bi2223/Ag tapes and YBCO coated conductors have the different properties about the dependence on the degree of external magnetic field. Therefore it is necessary to consider these characteristics of HTS tapes at magnet design stage. We proposed an optimal design method for superconducting coils using Bi2223/Ag tapes. And the proposed configuration is optimized by using the simulated annealing (SA), which is one of the optimization algorithms, under a lot of constraints such as B-I characteristic, storage energy, and so on. The details of the optimization method and an example of its application to SMES coils (72 NU) using YBCO coated conductors are shown.
  • Spasov, V, S Noguchi, H Yamashita
    IEEE TRANSACTIONS ON MAGNETICS 39 3 1685 - 1688 2003年05月 [査読有り][通常論文]
     
    A fast magnetostatic field analysis by the three-dimensional (3-D) geometric multigrid method with edge hexahedra is presented. The multigrid method uses a symmetric Gauss-Seidel smoother with conjugate gradient acceleration. The convergence and the speed of the V- and W-cycle multigrid method using this smoother are compared with the multigrid using Gauss-Seidel. Comparison is also made with the finite-element method (FEM)using ICCG. The multigrid with the accelerated symmetric Gauss-Seidel shows a stable convergence rate that does not deteriorate for bad quality meshes. It is, much faster than the conventional multigrid with Gauss-Seidel and the FEM using ICCG.
  • S Noguchi, F Kanagawa, H Yamashita
    IEEE TRANSACTIONS ON MAGNETICS 39 3 1646 - 1649 2003年05月 [査読有り][通常論文]
     
    We have been developing a tracking and steering system, which can successively observe numerical data during the numerical computation and can change parameters in the numerical analysis. Moreover, the proposed system is also developed to connect computers in the network: one for numerical computation, the other, for visualization, tracking, and steering of the numerical computation. In this paper, we propose two kinds of systems with different methods of communication between computers. One is the application software client, where the computers are directly communicated by using TCP/IP. Another is the web browser client, where the web server and web browser are necessary. The proposed system enables users to control the numerical computation from everywhere.
  • 松友 真哉, 野口 聡, 山下 英生, 谷本 茂也
    電気学会論文誌. D, 産業応用部門誌 = The transactions of the Institute of Electrical Engineers of Japan. D, A publication of Industry Applications Society 123 4 364 - 369 一般社団法人 電気学会 2003年04月01日 [査読無し][通常論文]
     
    The permanent magnet motors (PM motors) are widely used in electrical machinery, such as air conditioner, refrigerator and so on. In recent years, from the point of view of energy saving, it is necessary to improve the efficiency of PM motor by optimization. However, in the efficiency optimization of PM motor, many design variables and many restrictions are required. In this paper, the efficiency optimization of PM motor with many design variables was performed by using the voltage driven finite element analysis with the rotating simulation of the motor and the genetic algorithm.
  • 野口 聡, 金川 文寛, 山下 英生
    シミュレーション 22 1 62 - 70 日鉄技術情報センタ- 2003年03月15日 [査読無し][通常論文]
     
    In this paper, we have proposed a tracking and steering system for numerical analysis in network environment. With development of the software and hardware technology on computer, the numerical analyses for huge and complex models have been performed. However, the numerical computations of such models are timeconsuming, and there is high possibility to mistake to input the data of model. Therefore, the steering technique, which is to visualize the physical quantity in calculating, and the tracking technique, which is to control the parameter in order to modify or improve the mistake, are necessary to reduce computing costs. Moreover, in the proposed system, the tracking and the steering can be performed from anywhere through the internet.
  • S Nagakura, S Noguchi, H Yamashita, Cingoski, V
    IEEE TRANSACTIONS ON MAGNETICS 38 2 417 - 420 2002年03月 [査読無し][通常論文]
     
    In this paper, a method for automatic hexahedral (Hex) mesh generation is presented. In this method, the shape recognition technique and the tree method are used. Utilizing the shape recognition technique, a mesh is generated in a complicated analysis domain, and a high-quality Hex mesh is obtained. By using the tree method, control of the mesh density is easily enabled. In this proposed system, a modest amount of input data is necessary, like object parameters and the mesh density data.
  • S Noguchi, H Yamashita, A Ishiyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 12 1 1459 - 1462 2002年03月 [査読無し][通常論文]
     
    This paper describes an optimal design method for SMES coils wound with high temperature superconducting (HTS) tapes (e.g., Bi2223/Ag tapes). Recently, the properties of HTS tapes have advanced and HTS magnets have been constructed and demonstrated [1]-[3]. However, the HTS tapes have thermal different characteristics compared with the low temperature superconducting (LTS) wires. Therefore, it is necessary to consider these characteristics of HTS tapes at magnet design stage. We propose an optimal design method for SMES coils using Bi2223/Ag tapes. And the proposed configuration is optimized by using the simulated annealing, (SA), which is one of the optimization algorithms, under a lot of constraints such as B-I characteristic, storage energy, and so on. The details of the optimization method and examples of its application to small SMES coils (0.5 MJ) using Bi2223/Ag tape are shown.
  • Yoshihiro Hosokawa, So Noguchi, Hideo Yamashita, Shigeya Tanimoto
    Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi) 138 63 - 71 2002年02月01日 [査読無し][通常論文]
     
    We propose a concept of evolvable analog LSIs and apply it to Intermediate Frequency (IF) filters, which are widely used in cellular phones. The developed chip can correct discrepancies in the values of analog circuit components by genetic algorithms (GAs), which have attained (1) a yield rate of 97%, (2) a 60% reduction of the filter area, and (3) a 38% reduction of power dissipation, compared with AKM commercial products. When analog Integrated Circuits (ICs) and Large-Scale Integrated Circuits (LSIs) are manufactured, the values of the analog circuit components, such as resistors or capacitors, often vary from the precise design specifications. Analog LSIs with such defective components cannot perform at required levels and thus have to be discarded. However, our technique can improve yield rates of analog LSIs and has two additional advantages, namely, smaller circuits and less power dissipation, which can lead to cost reductions and efficient implementation of analog LSIs: This approach could be applied to a wide variety of analog LSIs. © 2001 Scripta Technica, Electr. Eng. Jpn.
  • 坪田 克己, 野口 聡, 山下 英生
    電気学会論文誌. D, 産業応用部門誌 = The transactions of the Institute of Electrical Engineers of Japan. D, A publication of Industry Applications Society 121 10 1017 - 1023 一般社団法人 電気学会 2001年10月01日 [査読無し][通常論文]
     
    In this paper, the convergency of the multigrid method for electromagnetic field computations is presented. The convergency and computational time of three multigrid algorithms (V-cycle, W-cycle and Full multigrid) are discussed and compared with each other. A comparison of the computational time between the multigrid method and the ICCG method, which is commonly used solution method in the finite element analysis, is also presented. It is proven that the convergency of the multigrid methods is better than that of the ICCG method especially for solving the large system.
  • 細川佳寛, 野口聡, 山下英生, 谷本茂也
    電気学会論文誌 D 121 2 171 - 177 2001年09月01日 [査読無し][通常論文]
     
    In optimal design of permanent magnet motor (PM motor), many design variables are required to consider some device properties. These variables are, for example, the shape of core and magnet, the teeth length, the number of turns, the winding radius, and so on. Moreover, many restrictions must be considered toward the practical PM motor design. These restrictions are, for example, the slot space factor, the cogging torque, and so on. However, the optimization problem, which has many design variables by using finite element method(FEM), has not been reported. In this paper, the efficiency of PM motor under considering described above is optimized by using FEM and optimization algorithm. In this problem, an objective function has many local minima and it is difficult to calculate its gradient. For these reasons, the genetic algorithm (GA) and the simulated annealing method(SA), which are stochastic method, are used for optimization method, becase of unnecessarity of the gradient and possibility of the global range search. Adding to both optimization methods, in this paper, SA combined with GA is used for one of optimization methods. As the results, the solutions optimized by these methods are reasonable from engineering point of view. © 2001, The Institute of Electrical Engineers of Japan. All rights reserved.
  • S Nagakura, S Noguchi, K Kaneda, H Yamashita, Cingoski, V
    IEEE TRANSACTIONS ON MAGNETICS 37 5 3522 - 3525 2001年09月 [査読無し][通常論文]
     
    In this paper, a method for automatic quadrilateral (Quad) mesh generation using dynamic bubble system is presented. The proposed method can be separated into three separate computational processes: the first one generates nodes inside the analysis domain using physically-based system of bubbles, the second one for automatic generation of Quad finite elements using previously generated set of nodes, and the last process where the generated elements are smoothed using Laplacian smoothing operator. The proposed method is suitable and easy extendable for automatic meshing of a complex 3-D domains.
  • 横瀬 義雄, 野口 聡, 山下 英生
    日本AEM学会誌 = Journal of the Japan Society of Applied Electromagnetics 9 1 33 - 38 日本AEM学会 2001年03月10日 [査読無し][通常論文]
  • S Noguchi, M Yamashita, H Yamashita, A Ishiyama
    IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 11 1 2308 - 2311 2001年03月 [査読無し][通常論文]
     
    This paper describes an optimal design method for superconducting magnets wound with high temperature superconducting (HTS) tapes (e.g. Bi2223/Ag tapes). Recently, the properties of HTS tapes have been in advance and HTS magnets have been constructed and demonstrated [1]-[4]. However, the HTS tapes have thermal different characteristics compared with the low temperature superconducting (LTS) wires. Therefore it is necessary to consider these characteristics of HTS tapes at magnet design stage. We propose a new configuration of the superconducting magnets using Bi2223/Ag tapes. And the proposed configuration is optimized by using the simulated annealing (SA), which is one of the optimization algorithms, under a lot of constraints such as B-I characteristic, central magnetic filed, held homogeneity and so on. The details of the optimization method and an example of its application to 12-tesla superconducting magnet using Bi2223/Ag tape are shown.
  • 細川 佳寛, 野口 聡, 山下 英生, 谷本 茂也
    電気学会論文誌. D, 産業応用部門誌 = The transactions of the Institute of Electrical Engineers of Japan. D, A publication of Industry Applications Society 121 2 171 - 177 一般社団法人 電気学会 2001年02月01日 [査読無し][通常論文]
     
    In optimal design of permanent magnet motor (PM motor), many design variables are required to consider some device properties. These variables are, for example, the shape of core and magnet, the teeth length, the number of turns, the winding radius, and so on. Moreover, many restrictions must be considered toward the practical PM motor design. These restrictions are, for example, the slot space factor, the cogging torque, and so on. However, the optimization problem, which has many design variables by using finite element method (FEM), has not been reported. In this paper, the efficiency of PM motor under considering described above is optimized by using FEM and optimization algorithm. In this problem, an objective function has many local minima and it is difficult to calculate its gradient. For these reasons, the genetic algorithm (GA) and the simulated annealing method (SA), which are stochastic method, are used for optimization method, becase of unnecessarity of the gradient and possibility of the global range search. Adding to both optimization methods, in this paper, SA combined with GA is used for one of optimization methods. As the results, the solutions optimized by these methods are reasonable from engineering point of view.
  • Spasov, V, S Noguchi, H Yamashita
    APPLIED ELECTROMAGNETICS (III) 10 111 - 114 2001年 [査読有り][通常論文]
     
    Three methods for electromagnetic force computation using edge elements are analyzed - the virtual work method, the Maxwell stress tensor method and the nodal force method. The methods are applied to compute the force at different air gaps of a voltage-fed nonlinear ac contractor. A comparison is made from the viewpoint of accuracy, speed and computer implementation. The sensitivity of the Maxwell stress tensor method to the choice of the integration surface is investigated. The computed results are compared with measurements.
  • A Ishiyama, J Nakatsugawa, S Noguchi, H Kado, M Ichikawa
    ELECTRICAL ENGINEERING IN JAPAN 134 1 17 - 27 2001年01月 [査読無し][通常論文]
     
    The superconducting fault current limiter is expected to be the first application of high-Tc superconductors (HTSs) in power systems. To develop a magnetic shielding-type superconductor fault current limiter, we have carried out some fundamental experiments on the magnetic shielding characteristics of an HTS bulk cylinder. In this paper, the experimental results of magnetic flux penetration into Bi-2223 cylinders are shown. An ac magnetic field is applied to the sample by a primary winding (copper coil) excited by ac triangular- and sinusoidal-waveform currents in the frequency range from 0.1 Hz to 100 Hz. We also developed a finite element method computer program for evaluation of the dynamic electromagnetic behavior of the HTS cylinder in a time-varying external magnetic field. The results of computer simulations considering the voltage-current (E-J) characteristic are compared with experiments. Next we carried out a current-limiting test with a small limiter model, and the developed finite element method computer program successfully simulated the electromagnetic behavior in current-limiting operation. (C) 2000 Scripta Technica.
  • S Noguchi, H Yamashita, Y Matsubayashi, E Okayama
    INTERNATIONAL JOURNAL OF APPLIED ELECTROMAGNETICS AND MECHANICS 15 1-4 417 - 422 2001年 [査読無し][通常論文]
     
    A new interactive visualization system for education and design purposes in 2D electromagnetics is proposed. The proposed system using numerically computational results for several typical model configurations can display interactively electromagnetic field phenomena for any other model configuration bounded with the previously computed ones. It uses simple bilinear interpolation techniques in order to provide fast interactive display. This visualization system can be used for design purposes of problems with different model configurations and as an educational tool for teaching electromagnetics.
  • E Okayama, Cingoski, V, S Noguchi, K Kaneda, H Yamashita
    IEEE TRANSACTIONS ON MAGNETICS 36 4 995 - 999 2000年07月 [査読無し][通常論文]
     
    A new interactive visualization system for educational and design purposes in 2D electromagnetics is proposed, The proposed system using numerically obtained results for several typical model configurations can display interactively electromagnetic field phenomena for any other model configuration bounded with the previously computed ones, It uses simple bilinear interpolation techniques in order to provide fast interactive display. This visualization system can be used for design purposes of problems with different model configurations and as an educational tool for teaching electromagnetics.
  • Cingoski, V, R Tokuda, S Noguchi, H Yamashita
    IEEE TRANSACTIONS ON MAGNETICS 36 4 1539 - 1542 2000年07月 [査読無し][通常論文]
     
    In this paper a fast multigrid solution method for edge-based finite element magnetostatic held computation with nested meshes is introduced and its efficiency is investigated. Special prolongation and restriction matrices were constructed according to the nature of the edge based held approximation. The comparison of the computation speed between the multigrid method and the ICCG method is also presented, showing that the multigrid method is very promising as a fast solution method for large system of equations.
  • Eiji Okayama, Vlatko Cingoski, So Noguchi, Kazufumi Kaneda, Hideo Yamashita
    IEEE Transactions on Magnetics 36 4 990 - 994 2000年 [査読無し][通常論文]
     
    A new interactive visualization system for educational and design purposes in 2D electromagnetics is proposed. The proposed system using numerically obtained results for several typical model configurations can display interactively electromagnetic field phenomena for any other model configuration bounded with the previously computed ones. It uses simple bilinear interpolation techniques in order to provide fast interactive display. This visualization system can be used for design purposes of problems with different model configurations and as an educational tool for teaching electromagnetics. © 2000 IEEE.
  • Vlatko Cingoski, Ryutaro Tokuda, So Noguchi, Hideo Yamashita
    IEEE Transactions on Magnetics 36 4 1535 - 1538 2000年 [査読無し][通常論文]
     
    In this paper a fast multigrid solution method for edge-based finite element magnetostatic field computation with nested meshes is introduced and its efficiency is investigated. Special prolongation and restriction matrices were constructed according to the nature of the edge based field approximation. The comparison of the computation speed between the multigrid method and the ICCG method is also presented, showing that the multigrid method is very promising as a fast solution method for large system of equations. © 2000 IEEE.
  • 石山 敦士, 中津川 潤之介, 野口 聡, 門 裕之, 市川 路晴
    電気学会論文誌. B, 電力・エネルギー部門誌 = The transactions of the Institute of Electrical Engineers of Japan. B, A publication of Power and Energy Society 119 11 1201 - 1209 電気学会 1999年11月01日 [査読無し][通常論文]
  • M Tsuda, H Lee, S Noguchi, Y Iwasa
    CRYOGENICS 39 11 893 - 903 1999年11月 [査読無し][通常論文]
     
    We present Part 4 results of a comprehensive theoretical study of an "electromaglev" system, in which a high-temperature superconducting bulk YBCO sample is levitated stably in a DC magnetic field generated by magnet system underneath the floating object. An electromagnetic analysis, based on a three-dimensional finite element technique (FEM) applied to the current vector potential method, has been developed to determine the supercurrent distribution in a field-cooled (and hence trapped-flux) YBCO disk that levitates stably in a magnetic field generated by the magnet system. The supercurrent distribution thus de termined was in turn used to compute trapped-flux-induced field profiles of the disk and predict a "levitation current" in the magnet system at which the disk, initially resting on a support plate, begins to levitate. Agreement between computed field profiles and levitation currents and those measured in the experiment was excellent, validating the analysis itself and the method used to derive solutions. The analysis demonstrates that the supercurrent distribution within a trapped-flux disk is far more complicated than that derived from the Bean model for a long cylinder under a uniform axial magnetic field. It is used for a parametric study of the effects of disk dimensions (radius, thickness, radius/thickness ratio) and trapped-flux strength on supercurrent distribution and lift-to-weight ratio. The magnitude of the B-r component generated by the magnet system is very important for lift and it is shown that thinner disks rather than thicker disks can improve Lift-to-weight ratio. Because accuracy of the analysis is disk-size independent, small disks are time-efficient for performing the analysis. (C) 2000 Elsevier Science Ltd. All rights reserved.
  • J. Nakatsugawa, S. Noguchi, A. Ishiyama, H. Kado, M. Ichikawa
    IEEE Transactions on Applied Superconductivity 9 2 1373 - 1376 1999年 [査読無し][通常論文]
     
    The superconducting fault current limiter (SCFCL) is expected to be the first application of high-T c superconductors (HTSs) in power systems. To develop a magnetic shielding type superconducting fault current limiter, we have carried out some fundamental experiments concerning the magnetic shielding characteristics of an HTS bulk cylinder. In this paper, the experimental results of magnetic flux penetration into a Bi(2223) cylinder are shown. AC magnetic field is applied to the sample by a primary winding (copper coil) excited by AC triangular- and sinusoidal-waveform currents in the frequency range of 0.1 Hz to 100 Hz. We also developed a Finite Element Method (FEM) computer program for evaluation of the dynamic electromagnetic behavior of the HTS cylinder in a time-varying external magnetic field. The results of computer simulations considering the voltage-current (E-J) characteristic are compared with experiments. © 1999 IEEE.
  • S. Noguchi, A. Ishiyama, T. Satow, N. Yanagi
    IEEE Transactions on Applied Superconductivity 9 2 624 - 627 1999年 [査読無し][通常論文]
     
    Very large current composite superconductors have been considered and adopted to use in SMES coils and fusion applications, such as the Large Helical Device (LHD). These superconductors have large cross-sectional area of high purity aluminum stabilizer to improve their stability and to enhance the overall current density. Once a normal-zone is initiated in such a composite superconductor, the current transfers to the aluminum stabilizer according to the temperature distribution. The time constant of current diffusion in the stabilizer, however, is very long due to the low electrical resistivity of aluminum and the large conductor size. Therefore, an excess joule heat is generated in a small area near superconducting filaments and the temperature increases locally. In this paper, to evaluate this peculiar property we carry out some simulations with regard to quench process in the superconductor applied to the helical coil of LHD in National Institute for Fusion Science. The simulations by using a newly developed computer code are compared with the experimental results of the stability tests on the short samples of LHD conductor. Furthermore, we focus on the influence of the CuNi alloy clad adopted to the LHD conductor on the normal transition and normal-zone propagation properties. © 1999 IEEE.
  • 野口 聡, 石山 敦士
    電気学会論文誌. B, 電力・エネルギー部門誌 = The transactions of the Institute of Electrical Engineers of Japan. B, A publication of Power and Energy Society 118 10 1103 - 1109 電気学会 1998年10月01日 [査読無し][通常論文]
  • S. Noguchi, A. Ishiyama
    IEEE Transactions on Applied Superconductivity 7 439 - 442 1997年12月01日 [査読無し][通常論文]
     
    This paper describes an optimal design method for high-field and highly homogeneous superconducting magnet systems with hybrid iron and active shielding. The presented design technique is a combination of the equivalent magnetization current method for the computation of the magnetic field problem, which includes nonlinear and saturated iron, and the simulated annealing for solving the corresponding optimization problem. The equivalent magnetization current method is superior in estimating the field homogeneity at the center of the magnet systems. By using the simulated annealing, the positions of each coil are optimized as continuous design variables, while the number of turns and layers of the coil windings are treated as discrete design variables. In this paper, the detail of the algorithm and the example of its application to 9-tesla magnet system with hybrid iron and active shield are shown. © 1997 IEEE.
  • S. Noguchi, A. Ishiyama
    IEEE Transactions on Magnetics 33 1904 - 1907 1997年12月01日 [査読無し][通常論文]
     
    This paper describes an optimal design method for highly homogeneous superconducting magnet systems with ferromagnetic shield. The presented design technique is a combination of the equivalent magnetization current method for the computation of the magnetic field problem, which includes nonlinear and saturated iron, and the simulated annealing for solving the corresponding optimization problem. The equivalent magnetization current method is superior in estimating the field homogeneity of the center of the magnet systems. By using the simulated annealing, the positions of each solenoid coil are optimized as continuous design variables, while the number of turns and layers of the coil windings are treated as discrete design variables. The details of the algorithm and some examples of its application to 1.5-tesla magnet systems with three types of magnetic shielding are shown. © 1997 IEEE.
  • 野口聡, 石山敦士
    電気学会論文誌 B 116 7 804 - 811 1996年07月 [査読無し][通常論文]
  • 野口 聡, 石山 敦士
    電気学会論文誌. B, 電力・エネルギー部門誌 = The transactions of the Institute of Electrical Engineers of Japan. B, A publication of Power and Energy Society 116 7 804 - 811 一般社団法人 電気学会 1996年06月20日 [査読無し][通常論文]
     
    We have been developing optimal design methods for high-field multi-section superconducting magnets for MRI and NMR study using mathematical programing method. To enhance the central magnetic field homogeneity, notch coils are added outside of the main solenoid. In this design, there is difficulty that the distances between notches are continuous design variables while the number of turns and layers of the main solenoids and notch coils are discrete variables. So we tried to develop a method which can deal with such two kinds of design variables at the same time by applying a modified simulated annealing. However, its convergence is relatively slow. Therefore, we adopt the Genetic algorithm, which can obtaine an optimal solution quickly, and combine it with the modified simulated annealing. Furthermore, we developed those method so as to be applied to non-linear optimization problems with constraints, such as characteristics of superconductor (e. g. B-J characteristic), Lorentz force and so on. The details of the algorithm and several examples of its application to three-section superconducting magnets are shown.
  • S. Noguchi, A. Ishiyama
    IEEE Transactions on Magnetics 32 4 2655 - 2658 1996年 [査読無し][通常論文]
     
    Highly homogeneous and high-field superconducting magnets arc difficult to be designed for its optimal configuration, which has the minimum winding volume. In this paper, we proposed an optimal design method utilizing a modified Genetic algorithm, which is newly developed, to realize the minimum winding volume design for multi-section superconducting magnets. The detail of the algorithm and two examples of its application to three-section superconducting magnets are shown. © 1996 IEEE.
  • S Noguchi, A Ishiyama
    PHYSICA B 216 3-4 212 - 214 1996年01月 [査読無し][通常論文]
     
    It is important for superconducting utilization, such as MRI, that superconducting magnets generate a highly homogeneous magnetic field. In order to enhance the field homogeneity, some notches are placed outside of a solenoid. The optimal design of notched solenoid arrangement becomes a problem which has both continuous and discrete design variables. In this paper, we propose an optimal design method utilizing a modified simulated annealing algorithm to realize the minimum winding volume design for notched multi-section superconducting magnets.

書籍

  • シミュレーション辞典
    野口 聡 (担当:分担執筆)
    2012年

講演・口頭発表等

その他活動・業績

特許

受賞

  • 2005年 優秀論文発表賞

共同研究・競争的資金等の研究課題

  • 超高磁場発生のための高耐久高安定マグネットの開発技術および経済性運転技術の確立
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2020年04月 -2024年03月 
    代表者 : 野口 聡, 金 錫範
  • 磁気アルキメデス法による海中マイクロプラスチック回収装置の概念設計
    日本学術振興会:科学研究費助成事業 挑戦的研究(萌芽)
    研究期間 : 2020年07月 -2023年03月 
    代表者 : 野口 聡
  • 日本学術振興会:科学研究費助成事業 基盤研究(S)
    研究期間 : 2018年06月 -2023年03月 
    代表者 : 石山 敦士, 植田 浩史, 野口 聡, 東 達也, 福田 光宏, 鷲尾 方一
     
    本研究の目標は、進行がんへの効果が期待される核医学治療用α線放出RI(211At)の多量・安定・分散生産のための加速器「高温超伝導スケルトン・サイクロトロン(HTS-SC)」を開発することである。そして本研究課題では、ビーム加速に必要な磁場を高精度に形成するための高温超伝導マルチコイルシステムを実現する5-High技術(高機械強度・高電流密度・高熱的安定・高磁場・高精度磁場)を統合した革新的コイル化技術の確立を目指す。2018年度(初年度)の主な成果としては、まず2021年・22年度に試作・実験を予定している「小型モデル(Baby-HTS-SC)」用と、実規模HTS-SC用のマルチコイルシステムの試設計(制約条件付き非線形最適化)を行った。また5-High統合コイル化技術について、1)高機械強度化技術:提案した「Super-ROROIコイル構造」の有効性を検証するため、Baby-HTS-SC用マルチコイルシステムを対象として、三次元電磁場・構造連成解析を実施し、コイル変形や発生磁場精度への影響等を明らかにした。2)高電流密度化と高熱的安定化を両立する技術(無絶縁コイル技術):実応用を想定して、複数の無絶縁REBCOコイルを積層したコイルシステムの局所的常伝導転移時の熱的・電磁的振舞いを、数値解析と小型モデルコイルシステムの試作・実験により評価した。解析は実験をよく再現でき、無絶縁コイルシステム特有の過渡特性を明らかにできた。3)高精度の磁場を発生する技術(遮蔽電流磁場の低減):実証実験用Baby-HTS-SC用マルチコイルシステムについて、自作の三次元非線形過渡電磁場解析プログラムを用いて、遮蔽磁場の影響を明らかにした。また、遮蔽電流磁場の空間分布と時間安定度への影響を低減する方法として、線材細線化法と電流波形制御法について、数値解析により低減効果を評価し良好な結果を得た。
  • 次世代医療用高温超伝導スケルトン・サイクロトロンの設計原理・開発基盤の確立
    日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2018年04月 -2022年03月 
    代表者 : 石山 敦士, 植田 浩史, 野口 聡, 福田 光宏, 鷲尾 方一
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2016年04月 -2019年03月 
    代表者 : 野口 聡, 宮尾 亮介
     
    次世代MRI/NMRの磁場補正技術の基礎検討を実施した。現在、世界的に第二世代超伝導体を使用した高磁場マグネットが開発されており、20テスラ以上の高磁場発生に成功している。そして、MITでは30.5テスラのNMR用マグネットが、日本でも9.4テスラのMRI用マグネットの開発が進められている。それらの次世代MRI/NMRマグネットで問題となっている、遮蔽電流による不正磁場の低減を検討してきた。また、遮蔽電流磁場を低減する手法を検討する前に、高精度かつ高速に磁場均一度を計算する手法および遮蔽電流を計算する手法も開発した。
  • 日本学術振興会:科学研究費助成事業 基盤研究(A)
    研究期間 : 2014年06月 -2018年03月 
    代表者 : 石山 敦士, 金 錫範, 植田 浩史, 山川 宏, 野口 聡
     
    重粒子線がん治療用超伝導加速器「先進ハイブリッド・サイクロトロン(AHC)」の開発を目標に、その実現の鍵となる5H(High):高機械強度・高電流密度・高安定・高磁場・高精度磁場を可能とするREBCO高温超伝導コイル開発のための基盤技術の確立を目指してきた。そして、高強度化・高磁場化のための「Super-YOROIコイル構造」、高電流密度化と高熱的安定化の両立のための「無絶縁コイル巻線方式」、そして高精度磁場化のための「遮蔽電流磁場の低減法」について有効性を数値解析と実験により検証した。
  • 日本学術振興会:科学研究費助成事業 国際共同研究加速基金(国際共同研究強化)
    研究期間 : 2016年 -2018年 
    代表者 : 野口 聡, 岩佐 幸和, Hahn Seungyong, Larbalestier David, 宮尾 亮介
     
    高温超伝導体で超高磁場を発生し、MRIやNMRなどに応用できれば、医療や製薬分野での大きな進展が期待できる。そこで、これまでに超伝導磁気センサ(SQUID)を高性能化するために開発してきた電磁界シミュレーション・ツールを、高磁場発生用マグネットの解析に応用した。超高磁場発生用高温超伝導マグネットでは、近年提案された無絶縁巻線技術が非常に効果的である一方、非常に複雑な現象を引き起こし、解析で挙動を明らかにすることが求められてきた。そこで、電磁気、熱、応力の連成シミュレーション・ツールを新たに開発した。世界最高DC磁場(45.5テスラ)の発生に成功する共に、解析によりその電磁的挙動を明らかにした。
  • 日本学術振興会:科学研究費助成事業 挑戦的萌芽研究
    研究期間 : 2014年04月 -2016年03月 
    代表者 : 石山 敦士, 野口 聡, 植田 浩史, 山川 宏
     
    本研究の最終目標は、高レベル放射性廃棄物の処理を可能とする「30MW級超伝導陽子加速器の開発」である。本提案課題では、REBCO高温超伝導線材と、筆者らが多くの実績を積み重ねてきた超伝導コイル化技術を活用することを前提に、筆者らが先行研究で提案した新しいサイクロトロン方式を採用した30MW級超伝導陽子加速器の主要素である超伝導コイルシステムの実規模設計を試みた。そしてその結果に基づき、現状技術の到達点評価を行うとともに、さらなる開発の必要性の高い高機械強度化に焦点を絞り、数値構造解析に基づき、2GPa以上の励磁時のフープ応力に耐え得る構造について検討を行った。
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2013年04月 -2016年03月 
    代表者 : 野口 聡
     
    磁気センサである超電導磁束干渉素子(SQUID)の高性能化のために、新しい電磁場解析手法を開発した。開発した電磁場解析では、磁束量子化という特殊な現象が表現できるようになった。さらに、最適化設計手法として、より堅固な手法を提案し、SQUIDの薄膜磁気シールドの最適化設計を可能にした。そして、今後のノイズ低減化を目的として、ミクロスケールの磁束挙動シミュレーション手法も開発した。
  • 日本学術振興会:科学研究費助成事業 若手研究(B)
    研究期間 : 2011年 -2012年 
    代表者 : 野ロ 聡
     
    磁気クロマトグラフィによる蛋白質分離のための磁気カラムを開発するために、高精度な磁場・流体連成シミュレーション・ツールを開発した。磁場と流体を同時に扱うマルチ・フィジックス・シミュレーション・ツールを開発する上で、蛋白質と磁気カラム、そしてマグネットのスケールの差が著しく異なるマルチ・スケールを考慮して、開発を行った。本研究では、蛋白質分離を考慮するために、従来はできなかった異種の蛋白質を同時にシミュレーション上で考慮することを可能にし、蛋白質分離の様子をシミュレーションできるようにした。
  • 日本学術振興会:科学研究費助成事業 若手研究(B)
    研究期間 : 2008年 -2010年 
    代表者 : 野口 聡
     
    高精度な磁場・磁性流体シミュレーション・ツールの開発を行なった.具体的なツール開発としては,磁場と磁性流体のマルチフィジックス・シミュレーション・ツールの開発を行ない,ナノスケール磁性微粒子と外部コイルの高精度マルチスケール・シミュレーション・ツールの開発を行なった.開発したシミュレーション・ツールの精度を実験と比較することで検証を行なった.さらに,シミュレーションの高速化を目指し,並列化計算への対応を図った.これにより,高速に高精度な磁場・磁性流体シミュレーションが行えるようになった.
  • 磁性流体のシミュレーション
    研究期間 : 2008年
  • 日本学術振興会:科学研究費助成事業 若手研究(B)
    研究期間 : 2006年 -2007年 
    代表者 : 野口 聡
     
    超伝導マグネットの実用的な設計を磁場解析・熱解析・最適化手法の連成により行えるようにするために,「堅固な設計」と「多目的設計に対する最適設計」についての検討を行った.「堅固な設計」については,Immune Algorithmを堅固な設計用に修正し,その修正法を用いることで,大幅な計算時間の短縮化も達成できた.また,「多目的設計に対する最適設計」ついては,ゲーム理論の適用により,トレードオフの関係にある多数の目的を考慮することが可能となった.さらに,協力ゲームや非協力ゲームなどの種々のゲーム理論を比較し,最適化設計に適したゲーム理論の調査を行った. 実験結果から冷凍機伝導冷却を使用した場合の,超伝導コイル内部で温度差を考慮に入れた設計手法についての検討も行った.超伝導マグネットを設計する上で,超伝導導体の特性を高精度にモデル化し,シミュレーションに組み込むことは必要不可欠である.そこで,高精度モデル化に必要な特性を,特に熱特性を対象とし実験計測を行った.この結果を磁場解析と熱解析の連成シミュレーションのためのプログラム・コードに組み込み,冷凍機伝導冷却特性を考慮したプログラム・コードへと発展させた.そして,そのプログラム・コードに最適化設計アルゴリズムを組み合わせることで,熱特性までも考慮に入れた超伝導マグネットの最適化設計を可能にした. 超伝導マグネットの最適化設計の結果,従来の熱特性を考慮していなかった設計結果よりも巻線体積をおよそ15%減らす設計に成功した.
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2005年 -2006年 
    代表者 : 山下 英生, 野口 聡, 三好 孝治
     
    物理現象のシミュレーション結果や本来不可視な現象を可視化するための種々の可視化手法の開発がさかんに進められている。しかし、現状の可視化システムは視覚情報のみを駆使するものであった。一般に電磁現象は、その空間の中に鉄心などを挿入すると電磁力が働く。観察者がこの電磁力を触覚により認識できるようであれば、視覚情報、触覚情報の両面から電磁現象を体感できることになり、研究者への感性の刺激は向上する。本研究では、観察者の感性を視覚、触覚の両面から刺激するインターラクションシステムをバーチャルリアリティ空間に実現するために、今年度、下記の研究開発を行った。 (1)触覚機能を活用した3次元分布情報(磁束線)とのインターラクションシステムの開発: 3次元磁場を可視化するための重要な情報に磁束線がある。この磁束線を3次元空間に、磁束密度が観察者に認識できるように適切に配置することが重要である。このようなアルゴリズムは存在しておらず、新しい方法の開発が必要である。本年度この手法の開発に取り組んだ。その成果を、電気学会誌に投稿中である。さらにこの磁束線を触覚センサーでタッチすることにより、バーチャル電磁空間内における電磁力を観察者に感知させる手法の開発が必要である。 (2)より精度の高い3次元磁場解析を実行するための六面体要素生成アルゴリズムの開発: バーチャル磁場空間の正確な情報を計算するためには、3次元磁場解析の精度の向上が必要である。そのためには、有限要素解析における適切な大きさの要素を適切な位置に配置する六面体要素自動生成技術が必須であり、その開発を行い、IEEE Transaction on Magneticsに発表した。 (3)指定した精度での磁場解析を行うアダプティプ有限要素法の開発: 3次元有限要素解析の解析結果の精度を補償するためのアダプティブ有限要素解析手法の開発を行った。磁界の回転をベースとして誤差を推定する方法である。その成果を、IEEE Transaction on Magneticsに発表した。
  • An Optimal Design Method for Superconducting Magnets
    Grant-in-Aid for Scientific Research
    研究期間 : 2006年
  • 日本学術振興会:科学研究費助成事業 若手研究(B)
    研究期間 : 2004年 -2005年 
    代表者 : 野口 聡
     
    系統安定化用超伝導エネルギー貯蔵装置(SMES)のためのコイルの形状最適化についての検討を行った。超伝導コイルを安定に運転させるためには、磁界-電流密度特性(B-J特性)などの超伝導特有の性質を考慮し、設計を行わなければならない。その際に、トロイダルコイル等は形状が複雑なことから、数値解析による評価が必要となる。さらに、高価な超伝導導体の使用量を削減するために、最適化アルゴリズムを導入することで、形状最適化設計を行い、その手法を確立した。 また、大型コイルになると、コイル内で温度差が生じることもあることから、それらを考慮し、温度異存する磁界-電流密度特性(B-J特性)を考慮することで、実用的な設計手法へと発展させた。さらに、磁場解析に時間を要することから、PCクラスタを使用することで、時間の短縮を試みた。 実例として、72MJ蓄積できるトロイダルコイルの最適化設計を行った。そして、構成されるコイルが8個から24個までを最適化設計し、その高温超伝導導体使用量と漏れ磁界などを比較した。その結果、8〜10個では導体使用量も多く、漏れ磁界も大きいが、12個以上では違いがほぼ無く、導体使用量は少なく、漏れ磁界も小さかった。また、同蓄積容量のマルチポールコイルと比較したときに、トロイダルコイルは導体使用量で85%に、漏れ磁界でも大きく低減できており、トロイダルコイルの性能の良さが示せた。 このように、磁場解析と最適化アルゴリズムを併用することで、超伝導固有の特性を考慮した上で、超伝導エネルギー貯蔵装置の形状最適化設計を可能にした。
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2003年 -2005年 
    代表者 : 五十嵐 一, 野口 聡, 渡辺 浩太
     
    本研究では,電気機器解析のための有限要素モデルを自動生成する学習機械を開発した.まず粗い初期メッシュをつくり,それを細分化することで目的の有限要素メッシュを生成する方法(以下,シンプル法と呼ぶ)を検討した.メッシュ生成過程では,磁束密度の大きさや角点からの距離などの特徴量の重み付き線形結合であるpを用い,pの大きな要素は誤差が大きいと推定して,その要素を分割する.そして最も誤差の少ない有限要素メッシュが得られる線形結合の重みを遺伝的アルゴリズムにより決定する.さらにこの係数を他の類似なモデルの有限要素メッシュ生成に用いる.このシンプル法により実際に有限要素メッシュを生成した結果,得られる有限要素メッシュの質が保障されず,扁平な要素が含まれてしまうことが判明した. 上の問題点を解消するために,要素の最長辺の長さからその適切な分割数を計算する「メッシュ制御法」を開発した.また要素の分割を行うか行わないかの判断を合理的に行うための指標を導入した.この方法を2次元の磁気ヘッドモデルに適用して有限要素メッシュを生成したところ,角度比によるメッシュ特性評価においては,評価関数の平均がシンプル法は0.251であったのに対して,メッシュ制御法では0.466となり,メッシュ特性の向上が確認できた.また,半径比によるメッシュ特性評価においても,評価関数の平均が,これまでシンプル法は0.455であったのに対して,メッシュ制御法では0.787となり,メッシュ特性の向上が確認できた.しかしこの方法によっても,初期の粗いメッシュの影響をうけるため,初期メッシュの形状が扁平な場合には,よい結果を得ることができなかった. そこで初期メッシュを用いるのではなく,節点濃度をバブル法により制御する「バブル法」を開発した. 本法を用いることにより精度をメッシュ制御法よりも向上させることができ,また初期メッシュによらない安定した質のよい有限要素メッシュを得ることができた.
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2003年 -2004年 
    代表者 : 山下 英生, 野口 聡, 金田 和文
     
    現状の可視化システムは視覚情報のみを駆使するものであった。一般に電磁現象は、その空間の中に鉄心などを挿入すると電磁力が働く。また、3次元空間中に表示した磁束線に沿っても力が働いており、これらを観察者が触覚により認識できれば、視覚情報、触覚情報の両面から電磁現象を体感できることになり、研究者、学生への感性の刺激はさらに向上する。本研究代表者は、以前から触覚情報を併用する2次元システムの開発を行い、視覚と触覚情報の併用が有効なことを確認した。本研究では、観察者の感性を視覚、触覚の両面から刺激するインターラクションシステムを3次元VR空間に実現するために下記の研究開発を行った。 (1)3次元触覚機能を活用した3次元空間分布情報とのインターラクションシステムの開発: バーチャル電磁空間内における電磁力を観察者に感知させる一方法として、空間中の鉄心をPhantom触覚センサーにより操作することにより、鉄心が受ける電磁力を直接観察者の手に感ずるシステムの開発を行った。さらに、観察者が鉄心を操作することにより、空間の物理量分布(磁束密度分布・磁束線)が変化する状況をステレオで実感できるインターラクティブシステムの開発を行った。 (2)電磁力計算アルゴリズムの開発: 3次元空間に分布する電磁場内に挿入された鉄心や電流には電磁力が働く。この電磁力計算とそのベクトルにより触覚センサーを動作させるアルゴリズムを開発した。 (3)インターラクションシステムのGUIの開発: 3次元空間に分布する物理量の観察において、視覚による情報のみでなく、触覚による情報を加味したインターラクションシステムを開発するには、観察者に親切なユーザーインターフェースが完備されることが必要であり、その開発を行った。 (4)リアルタイム応答を実現するためのアルゴリズムおよびデータ構造の開発: (2)の電磁力を観察者が触覚により認知するためには、バーチャル3次元空間内で観察者のアクションに応答して、リアルタイムに反応しなければならない。すなわち、インタラクティブに電磁空間にアクセスしながら、思考の中断が起きないように高速度でかつ正確に応答する必要があり、そのためのアルゴリズムとデータ構造の開発を行った。
  • 日本学術振興会:科学研究費助成事業 若手研究(B)
    研究期間 : 2002年 -2003年 
    代表者 : 野口 聡
     
    本研究は,温酸化物超伝導体の電磁界および熱解析の連成問題の高精度化と最適化設計手法を用いた超伝導応用機器の特性改善のための検討が目的となっている. 高温酸化物超伝導体の電磁界解析手法として,主にE-J特性を考慮した非線形有限要素法が使用されているが,解の収束性に問題がある.そこで,昨年度(H14年度)は,エレメント・フリー・ガラーキン法を導入し,解の収束性の改善を図った.その結果,ある程度の改善はみられたが,問題解決には至らなかった.そこで,該当年度(H15年度)は,有限要素法に対して,隣接要素の影響を考慮する改善手法を提案し,解の収束性の問題を解決し,提案手法の妥当性を検証した. さらに,高温酸化物超伝導体を使用した超電導エネルギー貯蔵装置(SMES)の最適化設計を試みた.まず,独自に開発してきた非線形最適化手法を用いた超伝導マグネットの手法に,高温酸化物超伝導テープ線材の持つ異方性を考慮することができるようにした.昨年度までは,Y系超伝導線材の異方性を考慮した新しい手法の提案を行った.該当年度は,この手法を基に,ソレノイドコイル,マルチポールコイル,トロイダルコイルなどのコイル形状に対して最適化設計を適用し,少ない体積で同量のエネルギーを蓄積できるマグネット形状を確認し,提案手法の有用性が確認できた。 これらの成果は,6th European Conference on Applied Superconductivityをはじめとする国内外の学会にて発表を行った.
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2001年 -2002年 
    代表者 : 山下 英生, 野口 聡, 金田 和文
     
    物理現象のシミュレーション結果や本来不可視な現象を可視化するための種々の可視化手法の開発がさかんに進められている。しかし、現状の可視化システムは視覚情報のみを駆使するものであった。一般に電磁現象は、その空間の中に鉄心などを挿入すると電磁力が働く。観察者がこの電磁力を触覚により認識できるようであれば、視覚情報、触覚情報の両面から電磁現象を体感できることになり、研究者への感性の刺激は向上する。本研究では、観察者の感性を視覚、触覚の両面から刺激するインターラクションシステムをバーチャルリアリティ空間に実現するために、下記の研究開発を行った。 1)3次元触覚機能を活用した3次元分布情報とのインターラクションシステムの開発: 第一スッテップとして、バーチャル電磁空間内における電磁力を観察者に感知させる一方法として、2次元空間中の鉄心を3次元触覚フィードバックデバイスにより操作することにより、鉄心に受ける電磁力をそのデバイスで受信するシステムの開発を行った。第二ステップとして、3次元空間中の鉄心を取り扱うようにシステム全体を完全3次元版に拡張した。すなわち、立体視アルゴリズムの開発を行い、さらにシステム全体の構築を行った。 2)電磁力計算アルゴリズムの開発: 3次元空間に分布する電磁場内に挿入された鉄心や電流には電磁力が働く。この電磁力計算とそのベクトルにより触覚センサーを動作させるアルゴリズムを開発した。 3)リアルタイム応答を実現するためのアルゴリズムおよびデータ構造の開発: 2)の電磁力を観察者が触覚により認知するためには、バーチャル3次元空間内で観察者のアクションに応答して、リアルタイムに反応しなければならない。すなわち、インタラクティブに電磁空間にアクセスしながら、思考の中断が起きないように高速度でかつ正確に応答する必要があり、そのためのアルゴリズムとデータ構造の開発を行った。
  • 日本学術振興会:科学研究費助成事業 奨励研究(A)
    研究期間 : 2000年 -2001年 
    代表者 : 野口 聡
     
    本研究は、高温酸化物超伝導体の電磁界および熱解析の連成問題と最適化アルゴリズムを用いた超伝導機器の特性改善が目的となっている。 高温酸化物超伝導体の電磁界解析手法として、種々の手法が提案されているが、E-J特性を考慮した場合に、解の収束性が悪くなるという特徴を有している。そこで、解析手法の改善を行った。その結果、従来方では解が収束しないような問題に対しても、提案手法は安定して解を求めており、かなりの改善が見られるようになった。また、酸化物バルク超伝導体表面上の磁束密度を計測する実験により、改善手法の妥当性を確認した。 さらに、高温酸化物超伝導体を使用した高均一磁場発生用、電力貯蔵用の超伝導マグネットの最適化設計を試みた。まず、独自に開発してきた非線形最適化手法を用いた超伝導マグネットの手法に、高温酸化物超伝導テープ線材の持つ異方性を考慮することができるようにした。従来の金属系超伝導体の場合は、コイル自体を半径方向に分割し(グレーディング)、外側のコイルほど大きいという設計が有効的であることが周知されていた。しかし、最適化アルゴリズムを導入し、高温酸化物超伝導体を使用した超伝導マグネットの最適化設計を行ったところ、内側のコイルほど長くした方が良いという、金属系とは反対の結果を得るにいたった。その結果、高温酸化物超伝導テープ線材の持つ異方性により、従来は巻線体積が増加せざるをえなかった形状に対して、巻線体積をおよそ75%に削減できることを示した。 これらの成果は、Applied Superconductivity Conferenceをはじめとする国内外の学会にて発表を行った。
  • 日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 1999年 -2000年 
    代表者 : 金田 和文, 野口 聡, 山下 英生
     
    本研究では、ドライブシミュレータやエンターテインメント映像等への応用に向けた水滴の流れのアニメーション手法を開発した。すなわち、水滴に働く遠心力や風力を考慮して水滴の流れのシミュレーションを行い、実写画像と合成することによりリアリスティックな表示を行うことのできる手法を開発した。これにより、人間が見て自然と感じる水滴の流れを表現することが可能となった。具体的には次の2点に関する手法の開発を行い、その有用性を検証するために水滴の流れのアニメーションを作成した。 1.物体表面からの落下を考慮した水滴の流れのシミュレーション法の開発: 自然な水滴の流れを実現するために、水滴の流れの物理現象を支配する主要な要素に着目し、離散化された物体表面上で重力、遠心力、風力等を考慮した流れのシミュレーション法を開発した。さらに、このシミュレーション法を3次元空間に拡張し、水滴に働く重力と界面張力を考慮することにより、表面からの落下を考慮した水滴の流れのシミュレーション手法を開発した。 2.実写画像と水滴との合成表示手法の開発: ビデオカメラから取り込まれた晴天時の実写画像を雨天時の画像に変換するため、実写画像を空領域、路面領域、そしてそれ以外の領域に分割し、それぞれの領域に応じた変換手法を用いて、雨天時の画像へ変換する手法を開発した。そして、これを背景画像として用いることにより、流れのシミュレーションによって発生させた水滴と合成表示する手法を開発した。この手法により、雨天時の水滴の流れのアニメーションを作成することが可能となった。
  • 電磁場解析結果の可視化
    研究期間 : 2000年
  • 電磁場解析手法に関する技術開発
    研究期間 : 2000年
  • メッシュ生成技術
    受託研究
    研究期間 : 2000年
  • 超電導バルク体の解析手法の開発
    研究期間 : 2000年
  • Sientific Visualization for Results of Numerical Computation
    研究期間 : 2000年
  • Development of Technique for Numerical Computation in Electromagnetics
    研究期間 : 2000年
  • Mesh Generation
    Funded Research
    研究期間 : 2000年
  • Development of Numerical Computation for Superconducting Bulk
    研究期間 : 2000年
  • 超伝導機器の最適化設計に関する研究
    日本学術振興会:科学研究費助成事業 特別研究員奨励費
    研究期間 : 1998年 -1998年 
    代表者 : 野口 聡
  • 電磁機器の最適化設計
    研究期間 : 1994年
  • An Optimal Design Method for Electromagnetic Apparatuses
    研究期間 : 1994年

教育活動情報

主要な担当授業

  • 電磁工学特論
    開講年度 : 2019年
    課程区分 : 修士課程
    開講学部 : 情報科学研究科
    キーワード : 偏微分方程式,電磁界解析,有限要素法,差分法,システム最適化,可視化
  • 電磁工学特論
    開講年度 : 2019年
    課程区分 : 修士課程
    開講学部 : 情報科学院
    キーワード : 偏微分方程式,電磁界解析,有限要素法,差分法,システム最適化,可視化
  • 電磁工学特論
    開講年度 : 2019年
    課程区分 : 博士後期課程
    開講学部 : 情報科学研究科
    キーワード : 偏微分方程式,電磁界解析,有限要素法,差分法,システム最適化,可視化
  • 電磁工学特論
    開講年度 : 2019年
    課程区分 : 博士後期課程
    開講学部 : 情報科学院
    キーワード : 偏微分方程式,電磁界解析,有限要素法,差分法,システム最適化,可視化
  • 電気制御システム演習Ⅱ
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : ロボットマニピュレータ、情報モデル化言語、電気機器
  • 電気機器学
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : モータ、発電機、エネルギー変換、アクチュエータ

大学運営

委員歴

  • 2011年   電気学会   北海道支部 総務企画幹事   電気学会
  • 2010年   電気学会   北海道支部 代議員   電気学会
  • 2009年   電気学会   調査専門委員会委員   電気学会
  • 2007年 - 2008年   電気学会   北海道支部 会計幹事   電気学会
  • 2007年 - 2008年   電気学会   調査専門委員会委員   電気学会
  • 2007年   低温工学・超電導学会   東北・北海道支部 幹事会委員   低温工学・超電導学会
  • 2005年 - 2006年   電気学会   調査専門委員会 幹事   電気学会


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